Flexible vibration module and display apparatus including the same

ABSTRACT

A flexible vibration module is disclosed. The flexible vibration module includes a piezoelectric composite layer, including: a plurality of piezoelectric portions each having a piezoelectric characteristic, where at least two of the plurality of piezoelectric portions have different sizes; and a flexible portion between the plurality of piezoelectric portions.

This application claims priority from and the benefit of Korean PatentApplication No. 10-2019-0037507 filed on Mar. 29, 2019, which isincorporated herein by reference in its entirety for all purposes as iffully set forth herein.

BACKGROUND Technical Field

The present disclosure relates to a display apparatus, and moreparticularly, to a flexible vibration module and a display apparatusincluding the same.

Discussion of the Related Art

In display apparatuses, a display panel displays an image, and aseparate speaker should be installed for providing sound. In somerelated art embodiments, a speaker is disposed in a display apparatus,and occupies a space. As a result, the design and spatial disposition ofthe display apparatus are limited.

A speaker applied to display apparatuses may be, for example, anactuator including a magnet and a coil. However, a thickness of theactuator is high. Therefore, it may be desirable to use piezoelectricelements that have lower thicknesses. Because a piezoelectric elementmay be brittle, piezoelectric elements may be easily damaged by externalimpact, thus the reliability of sound reproduction may be low.

SUMMARY

Accordingly, the present disclosure is directed to providing a flexiblevibration module and a display apparatus including the same thatsubstantially obviate one or more of the above-identified problems dueto limitations and disadvantages of the related art. A speaker appliedto a display apparatus may be a film type vibration module. The filmtype vibration module may be manufactured to have a large area and thusmay be applied to a large-area display apparatus. However, due to a lowvibration caused by a low piezoelectric characteristic, it may bedifficult to apply the film type vibration module to the large-areadisplay apparatus. Ceramic may be applied for enhancing a piezoelectriccharacteristic. As a result, durability may be weak and the size of theceramic may be limited.

Piezoelectric ceramic may be applied to a display apparatus in avibration module including a piezoelectric composite layer. As a result,the piezoelectric composite layer mainly vibrates in a horizontaldirection of the display apparatus. This may make it difficult tosufficiently vibrate the display apparatus in a vertical direction. As aresult, the display apparatus may be unable to output a desired sound toa forward region in front of the display apparatus. Alternatively, afilm type piezoelectric material may be applied to a display apparatus,causing a sound pressure characteristic of the display apparatus to belower than that of general speakers (e.g, exciters). In some exampleembodiments, a stacked film type piezoelectric—where a film typepiezoelectric is configured with a multilayer to improve a soundpressure—may be applied to a display apparatus. As a result, powerconsumption increases.

A vibration module may enhance a piezoelectric characteristic,stiffness, and flexibility. A vibration module may be formed of acomposite layer including a filler having a high dielectric constant anda low piezoelectric characteristic. As a result, the vibration modulemay be unable to realize a desired sound. In some example embodiments ofthe present disclosure, a vibration module may be formed ofpiezoelectric ceramic having a piezoelectric characteristic and formedof an organic material so as to enhance stiffness and flexibility.

In other example embodiments, a vibration module may be formed ofpiezoelectric ceramic having a piezoelectric characteristic and formedof a material such as a polymer to decrease the fragility of thepiezoelectric ceramic. In these example embodiments, the vibrationmodule may be configured so that the material such as a polymer is in apiezoelectric ceramic composite and the vibration module hasflexibility.

In other example embodiments, a vibration module may have variousvibration frequencies, a sound pressure characteristic may be enhanced,and a sound reproduction band may be enlarged. In these exampleembodiments, a display apparatus may include a vibration module having astructure for enhancing a piezoelectric characteristic, stiffness, andflexibility.

An aspect of the present disclosure is to provide a flexible vibrationmodule with an enhanced piezoelectric characteristic, stiffness, andflexibility and a display apparatus including the same. Another aspectof the present disclosure is to provide a flexible vibration module withan enhanced sound pressure characteristic and expanded soundreproduction band, based on various vibration frequencies, and a displayapparatus including the same. Another aspect of the present disclosureis to provide a display apparatus that outputs a sound, that isgenerated based on a vibration of a display panel, to a forward regionin front of the display panel.

To achieve these and other aspects of the inventive concepts, and inaccordance with the purpose of the present disclosure, as embodied andbroadly described, a flexible vibration module includes: a piezoelectriccomposite layer, wherein the piezoelectric composite layer includes: aplurality of piezoelectric portions each having a piezoelectriccharacteristic, wherein at least two of the plurality of piezoelectricportions have different sizes; and a flexible portion between theplurality of piezoelectric portions.

In another aspect of the present disclosure, a flexible vibration moduleincludes: a piezoelectric composite layer, wherein the piezoelectriccomposite layer includes: a plurality of piezoelectric portions eachhaving a piezoelectric characteristic; and a flexible portion betweenthe plurality of piezoelectric portions, wherein the piezoelectriccomposite layer has a plurality of vibration frequencies.

In another aspect of the present disclosure, a flexible vibration moduleincludes: a flexible vibration module, wherein the flexible vibrationmodule includes: a piezoelectric composite layer, wherein thepiezoelectric composite layer includes: a plurality of piezoelectricportions each having a piezoelectric characteristic, wherein at leasttwo of the plurality of piezoelectric portions have different sizes; anda flexible portion between the plurality of piezoelectric portions; anda display panel, wherein the display panel includes a display areaconfigured to display an image and vibrate according to a vibration ofthe flexible vibration module.

According to the present disclosure, most regions of the display panelmay vibrate by a film type large-area flexible vibration module. As aresult, localization of a sound based on the vibration of the displaypanel may be more enhanced, thereby realizing a stereo sound effect.Moreover, according to the present disclosure, the display panel mayvibrate according to various vibration frequencies to output a sound. Asa result, a sound pressure characteristic of the sound may increase anda sound reproduction band may expand.

It is to be understood that both the foregoing general description andthe following detailed description of the present disclosure areexemplary and explanatory, and are intended to provide furtherexplanation of the inventive concepts as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the disclosure and are incorporated in and constitute apart of this application, illustrate example embodiments of thedisclosure and together with the description serve to explain theprinciples of the disclosure. In the drawings:

FIG. 1 is a perspective view of a display apparatus according to a firstexample embodiment of the present disclosure.

FIG. 2 is a cross-sectional view taken along line I-I′ illustrated inFIG. 1.

FIG. 3 illustrates a flexible vibration module according to a firstexample embodiment of the present disclosure.

FIG. 4 is a cross-sectional view taken along line II-II′ illustrated inFIG. 3.

FIG. 5 illustrates a flexible vibration module according to a secondexample embodiment of the present disclosure.

FIG. 6 illustrates a flexible vibration module according to a thirdexample embodiment of the present disclosure.

FIG. 7 illustrates a flexible vibration module according to a fourthexample embodiment of the present disclosure.

FIG. 8 is a cross-sectional view taken along line III-III′ illustratedin FIG. 7.

FIG. 9 illustrates a flexible vibration module according to a fifthexample embodiment of the present disclosure.

FIG. 10 is a cross-sectional view taken along line IV-IV′ illustrated inFIG. 9.

FIG. 11 illustrates a modified example embodiment of the flexiblevibration module illustrated in FIG. 9.

FIG. 12 is another cross-sectional view taken along line I-I′illustrated in FIG. 1.

FIG. 13 illustrates the flexible vibration module and partitionillustrated in FIG. 12.

FIG. 14 illustrates the flexible vibration module and partitionillustrated in FIG. 12.

FIGS. 15A to 15C illustrate modified example embodiments of the firstand second flexible vibration modules illustrated in FIG. 14.

FIGS. 16A to 16C illustrate various display apparatuses to which aflexible vibration module according to example embodiments of thepresent disclosure may be applied.

FIG. 17 is a graph showing a sound pressure characteristic of a displaypanel according to an example embodiment of the present disclosure and asound pressure characteristic of a display panel according to acomparative example.

DETAILED DESCRIPTION

Reference will now be made in detail to the example embodiments of thepresent disclosure, examples of which may be illustrated in theaccompanying drawings. Wherever possible, the same reference numberswill be used throughout the drawings to refer to the same or like parts.Advantages and features of the present disclosure, and implementationmethods thereof will be clarified through following example embodimentsdescribed with reference to the accompanying drawings. The presentdisclosure may, however, be embodied in different forms and should notbe construed as limited to the example embodiments set forth herein.Rather, these example embodiments are provided so that this disclosurewill be thorough and complete, and will fully convey the scope of thepresent disclosure to those skilled in the art.

A shape, a size, a ratio, an angle, and a number disclosed in thedrawings for describing example embodiments of the present disclosureare merely examples, thus the present disclosure is not limited to theillustrated details. Like reference numerals refer to like elementsthroughout. In the following description, when the detailed descriptionof the relevant known technology unnecessarily obscures important pointsof the present disclosure, the detailed description may be omitted.

Although the terms “first,” “second,” etc. may be used in the presentdisclosure to describe various elements, these elements should not belimited by these terms. These terms may be used to distinguish oneelement from another. For example, a first element may be termed asecond element, and, similarly, a second element may be termed a firstelement, without departing from the scope of the present disclosure. Theterm “at least one” may include any and all combinations of one or moreof the associated listed items. Features of various example embodimentsof the present disclosure may be partially or overall coupled to orcombined with each other, and may be variously inter-operated with eachother. The example embodiments of the present disclosure may be carriedout independently from each other, or may be carried out together inco-dependent relationship. Although the same elements may be illustratedin multiple drawings, like reference numerals may refer to likeelements. Also, for convenience of description, a scale of each ofelements illustrated in the accompanying drawings may differ from a realscale, and thus, is not limited to the scales illustrated in thedrawings.

FIG. 1 is a perspective view of a display apparatus according to a firstexample embodiment of the present disclosure, and FIG. 2 is across-sectional view taken along line I-I′ illustrated in FIG. 1. Asillustrated in FIGS. 1 and 2, the display apparatus according to anexample embodiment of the present disclosure may include a display panel100 and a flexible vibration module 300 disposed on a rear surface ofdisplay panel 100. Display panel 100 according to the present disclosuremay be a curved display panel or one of all types of display panels suchas a liquid crystal display panel, an organic light emitting displaypanel, a quantum dot light emitting display panel, a micro lightemitting diode display panel, and an electrophoresis display panel. Forexample, if display panel 100 according to the present disclosurevibrates by flexible vibration module 300 to generate a sound wave (or asound) or to generate a haptic feedback responding to a touch, displaypanel 100 is not limited to a specific display panel.

In some example embodiments, display panel 100 may include a thin filmtransistor (TFT) array substrate including a plurality of pixels definedby a plurality of gate lines and a plurality of data lines and a TFT ineach of the plurality of pixels to drive each of the plurality ofpixels, a light emitting device layer on the TFT array substrate, and anencapsulation substrate covering the light emitting device layer. Forexample, the encapsulation substrate may protect the TFT and the lightemitting device layer from an external impact and may prevent water frompenetrating the light emitting device layer. Display panel 100 mayinclude a display area that displays an image according to driving theplurality of pixels and a non-display area that surrounds the displayarea.

Display panel 100 may include a bending portion that is bent or curvedto have a curved shape or a certain curvature radius. The bendingportion of display panel 100 may be in at least one of one edge (orperiphery) and another edge (or periphery) of display panel 100 that areparallel to each other. These edges may include only the non-displayarea, or may include an edge or periphery of the display area and thenon-display area. In some example embodiments, display panel 100 mayinclude the bending portion provided by bending the non-display area andmay have a structure including a one-sided bezel bending structure or atwo-sided bezel bending structure. In other example embodiments, displaypanel 100 may include the bending portion provided by bending thenon-display area and may have a structure including a one-sided activebending structure or a two-sided active bending structure.

The display apparatus according to an example embodiment of the presentdisclosure may further include a functional film 130 disposed on displaypanel 100. Functional film 130 may be disposed on a front surface ofdisplay panel 100. In some example embodiments, functional film 130 maybe attached on a front surface of display panel 100 by a film adhesivemember. In some example embodiments, the film adhesive member mayinclude a pressure sensitive adhesive (PSA), an optically clear adhesive(OCA), or an optically clear resin (OCR). Functional film 130 mayinclude at least one of an anti-reflection layer (or an anti-reflectionfilm) for preventing reflection of external light, a barrier layer (or abarrier film) for primarily preventing penetration of water or oxygen,and a light path control layer (or a light path control film) forcontrolling a light path (or a viewing angle).

The display apparatus according to an example embodiment of the presentdisclosure may further include a touch panel (or a touch electrodelayer) for sensing a user touch applied to display panel 100. Forexample, the touch panel may be disposed to overlap the display area andmay act as a touch sensor for sensing the user touch applied to displaypanel 100. For example, the touch panel may be disposed between a lightemitting device layer and an encapsulation substrate, or may be disposedbetween display panel 100 and functional film 130. The touch panel mayinclude a plurality of touch electrodes for sensing a variation of acapacitance caused by the user touch based on a mutual capacitive typeor a self-capacitive type.

Flexible vibration module 300 may be disposed on a rear surface (or abackside) of display panel 100 and may vibrate display panel 100.Flexible vibration module 300 may be a thin film type that has variousvibration frequencies (or natural vibration frequencies, or naturalfrequencies) based on a piezoelectric characteristic and may haverelatively high flexibility. For example, flexible vibration module 300may have a thickness that is thinner than that of display panel 100.Flexible vibration module 300 may be referred to as a sound generatingmodule, a sound generating device, a film actuator, a film typepiezoelectric composite actuator, a film speaker, a film typepiezoelectric speaker, or a film type piezoelectric composite speaker.Flexible vibration module 300 may use display panel 100 as a vibrationplate.

Flexible vibration module 300 may be formed of piezoelectric ceramichaving a piezoelectric characteristic. To improve an impact resistanceof piezoelectric ceramic and to realize flexibility, flexible vibrationmodule 300 may be formed of a material such as a polymer inpiezoelectric ceramic. In some example embodiments, flexible vibrationmodule 300 may include piezoelectric ceramic having a perovskitecrystalline structure, and may vibrate (or exhibit mechanicaldisplacement) in response to an electrical signal applied from theoutside.

Flexible vibration module 300 may vibrate at various vibrationfrequencies according to an electrical signal. For example, flexiblevibration module 300 may vibrate according to a voice signalsynchronized with an image displayed by display panel 100 to vibratedisplay panel 100. A sound generated based on a vibration of displaypanel 100 may have a sound pressure characteristic that increases basedon a vibration having various vibration frequencies. The vibration offlexible vibration module 300 may expand a sound reproduction band. Inan example embodiment, the flexible vibration module 300 may be disposedon display panel 100 and may vibrate according to a haptic feedbacksignal (or a tactile feedback signal) synchronized with a user touchapplied to a touch panel (or a touch sensor layer) embedded into displaypanel 100 to vibrate display panel 100. Accordingly, display panel 100may vibrate based on a vibration of flexible vibration module 300 toprovide a user (or a viewer) with at least one of a sound and a hapticfeedback.

Moreover, flexible vibration module 300 according to an exampleembodiment may have a size corresponding to the display area of displaypanel 100. A size of flexible vibration module 300 may be 0.9 to 1.1times a size of the display area. For example, a size of flexiblevibration module 300 may be the same as or approximately equal to thatof the display area of display panel 100, thus flexible vibration module300 may cover most of display panel 100. A vibration generated byflexible vibration module 300 may vibrate a whole portion of displaypanel 100, thus localization of a sound may be high and satisfaction ofa user may be improved. A contact area (or panel coverage) betweendisplay panel 100 and flexible vibration module 300 may increase, thus avibration region of display panel 100 may increase. This improves asound of a middle to low pitch sound band generated based on a vibrationof display panel 100. In a large-sized display apparatus, a wholeportion of display panel 100 having a large size (or a large area) mayvibrate, thus localization of a sound based on a vibration of displaypanel 100 may be enhanced, thereby realizing a stereo sound effect.

In some example embodiments, flexible vibration module 300 may beattached to the rear surface of display panel 100 by an adhesive member200 (or a module adhesive member). Adhesive member 200 may be disposedbetween the rear surface of display panel 100 and flexible vibrationmodule 300. For example, adhesive member 200 may attach flexiblevibration module 300 on the rear surface of display panel 100 and may bean adhesive or a double-sided tape including an adhesive layer having ahigh adhesive force or attaching force. For example, the adhesive layerof adhesive member 200 may include epoxy, acryl, silicon, or urethane.The adhesive layer of adhesive member 200 may further include anadditive such as a tackifier or an adhesion enhancing agent, a waxcomponent, or an anti-oxidation agent. The additive may prevent orreduce the adhesive member 200 from being detached (or stripped) fromdisplay panel 100 by a vibration of vibration module 300. For example,the tackifier may be rosin derivative, the wax component may be paraffinwax, and the anti-oxidation agent may be a phenol-based anti-oxidationagent such as thiolester.

According to another example embodiment, adhesive member 200 may furtherinclude a hollow portion between display panel 100 and flexiblevibration module 300. The hollow portion of adhesive member 200 mayprovide an air gap between display panel 100 and flexible vibrationmodule 300. Due to the air gap, a sound wave (or a sound pressure) basedon a vibration of flexible vibration module 300 may not be dispersed byadhesive member 200 and may concentrate on display panel 100. Therefore,the loss of a vibration caused by adhesive member 200 may be minimizedor reduced, thereby increasing a sound pressure characteristic of asound generated based on a vibration of display panel 100.

The display apparatus according to an example embodiment of the presentdisclosure may further include a rear structure 500 that supportsdisplay panel 100. Rear structure 500 may be referred to as a rearcover, a cover bottom, a plate bottom, a back cover, a base frame, ametal frame, a metal chassis, a chassis base, or an m-chassis. Rearstructure 500 may be a supporter that supports display panel 100 and maybe an arbitrary type frame or a plate structure each disposed on a rearsurface of the display apparatus.

Rear structure 500 according to an example embodiment may include afirst rear cover 510 and a second rear cover 550. First rear cover 510may be a plate member covering the whole rear surface of display panel100. First rear cover 510 may be spaced apart from a rearmost surface ofdisplay panel 100 with a gap space GS therebetween. For example, gapspace GS may be referred to as an air gap, a vibration space, or a soundbox. Second rear cover 550 may be a plate member that is disposed on arear surface of first rear cover 510 to cover the whole rear surface offirst rear cover 510.

First rear cover 510 and second rear cover 550 according to an exampleembodiment may be coupled or connected to each other by a coverconnection member 530. For example, cover connection member 530 may bean adhesive resin, a double-sided adhesive tape, or a double-sidedadhesive foam pad, and may have elasticity for absorbing an impact. Forexample, the cover connection member 530 may be disposed in a wholeregion between the first rear cover 510 and the second rear cover 550.In another example embodiment, the cover connection member 530 may be ina mesh structure including an air gap between the first rear cover 510and the second rear cover 550.

The display apparatus according to an example embodiment of the presentdisclosure may further include a middle frame 600. Middle frame 600 maybe disposed between a rear edge or a rear periphery of display panel 100and a front edge or a front periphery of rear structure 500. Middleframe 600 may support an edge or a periphery of each of display panel100 and rear structure 500 and may surround a side surface of each ofdisplay panel 100 and rear structure 500. The middle frame 600 mayprovide a gap space GS between display panel 100 and rear structure 500.Middle frame 600 may include a middle cabinet, a middle cover, or amiddle chassis.

Middle frame 600 according to an example embodiment may include asupporting part 610 and a sidewall portion 630. Supporting part 610 maybe disposed between the rear edge or the rear periphery of display panel100 and the front edge or the front periphery of rear structure 500, andthus, may provide a gap space GS between display panel 100 and rearstructure 500. A front surface of supporting part 610 may be coupled orconnected to the rear edge or the rear periphery of display panel 100 bya first adhesive member 601, and a rear surface of supporting part 610may be coupled or connected to the front edge or the front periphery ofrear structure 500 by a second adhesive member 603. For example,supporting part 610 may have a tetragonal single frame structure, or mayhave a plurality of division bar shapes.

Sidewall portion 630 may be vertically coupled or connected to an outersurface of supporting part 610 in parallel with a thickness direction Zof the display apparatus. Sidewall portion 630 may surround all of anouter surface of display panel 100 and an outer surface of rearstructure 500 and may protect the outer surface of each of display panel100 and rear structure 500. Supporting part 610 and the sidewall portion630 according to an example embodiment may be coupled or connected toeach other to configure a single body, and thus, may have a framestructure having a perpendicular single-sided structure.

The display apparatus according to an example embodiment of the presentdisclosure may include a panel connection member instead of middle frame600. The panel connection member may be disposed between the rear edgeor the rear periphery of display panel 100 and the front edge or thefront periphery of rear structure 500 and may provide gap space GSbetween display panel 100 and rear structure 500. The panel connectionmember may be disposed between a rear edge or a rear periphery ofdisplay panel 100 and an edge or a periphery of rear structure 500 andmay attach display panel 100 to rear structure 500. For example, thepanel connection member may be a double-sided adhesive tape, asingle-sided adhesive tape, or a double-sided adhesive foam pad.

In some example embodiments, the display apparatus may include the panelconnection member instead of middle frame 600. Rear structure 500 mayinclude a sidewall cover part that is bent from an end of second rearcover 550 and surrounds all of an outer surface (or an outer sidewall)of each of first rear cover 510, the panel connection member, anddisplay panel 100. The sidewall cover part according to an exampleembodiment may have a single sidewall structure or a hemming structure.The hemming structure may be structure where ends of an arbitrary memberis bent in a curved shape to overlap each other, or are spaced apartfrom each other in parallel.

The display apparatus according to an example embodiment of the presentdisclosure may output a sound generated based on a vibration of displaypanel 100 caused by a vibration of flexible vibration module 300disposed on the rear surface of display panel 100. The sound may beoutput to a forward region FD in front of display panel 100, therebyenhancing immersion of a viewer watching an image displayed by displaypanel 100. Most regions of display panel 100 may vibrate by flexiblevibration module 300 having a film type and a large area. As a result,localization of a sound based on the vibration of display panel 100 maybe more enhanced, thereby realizing a stereo sound effect.

In some example embodiments, display panel 100 may vibrate according todriving of flexible vibration module 300 having various vibrationfrequencies to output a sound. As a result, a sound pressurecharacteristic of the sound may increase and a sound reproduction bandmay expand. In some example embodiments, even without configuring aseparate haptic driving apparatus, display panel 100 may vibrate basedon the vibration of flexible vibration module 300 disposed on the rearsurface of display panel 100 to provide a user with a haptic feedbackresponding to a user touch applied to display panel 100.

FIG. 3 illustrates a flexible vibration module 300 according to a firstexample embodiment of the present disclosure, and FIG. 4 is across-sectional view taken along line II-II′ illustrated in FIG. 3.FIGS. 3 and 4 illustrate the flexible vibration module illustrated inFIG. 2. As illustrated in FIGS. 3 and 4, flexible vibration module 300according to the first example embodiment of the present disclosure mayinclude a piezoelectric composite layer 310, a first electrode layer320, and a second electrode layer 330. Piezoelectric composite layer 310may be a thin film type that has various vibration frequencies (ornatural frequencies, or natural vibration frequencies) based on apiezoelectric characteristic or a plurality of vibration frequencies andmay have relatively high flexibility. Piezoelectric composite layer 310according to an example embodiment may include a plurality ofpiezoelectric portions 311 and a flexible portion 313 between theplurality of piezoelectric portions 311. The plurality of piezoelectricportions 311 and flexible portion 313 may be disposed on the same plane(or the same layer). For example, piezoelectric composite layer 310 maysecure a piezoelectric characteristic and flexibility.

Piezoelectric composite layer 310 may have various shapes, based on anarrangement structure of the plurality of piezoelectric portions 311 andflexible portion 313. For example, piezoelectric composite layer 310 mayhave a tetragonal shape, a circular shape, an elliptical shape, or apolygonal shape. Each of the plurality of piezoelectric portions 311 mayinclude a polygonal pattern. For example, the plurality of piezoelectricportions 311 may have a line pattern having a certain first width W1,may be spaced apart from one another in a first direction X, and may bein parallel in a second direction Y.

At least one of the plurality of piezoelectric portions 311 according toan example embodiment may have a different size. A size of each of theplurality of piezoelectric portions 311 may be defined as one of alength, a width, a thickness, a width, an area, and a volume. Forexample, some of the plurality of piezoelectric portions 311 may havethe same size within a process error range (or an allowable error range,or a tolerance) occurring in a manufacturing process, and the otherpiezoelectric portions 311 may have different sizes. In another exampleembodiment, the plurality of piezoelectric portions 311 may havedifferent sizes. For example, at least one of the plurality ofpiezoelectric portions 311 may have a different length, a differentwidth, or a different thickness.

According to another example embodiment, at least one of the pluralityof piezoelectric portions 311 may have a different vibration frequency.For example, some of the plurality of piezoelectric portions 311 mayhave the same vibration frequency, and the other piezoelectric portions311 may have different vibration frequencies. In another exampleembodiment, the plurality of piezoelectric portions 311 may havedifferent vibration frequencies, respectively.

The plurality of piezoelectric portions 311 may have a horizontalsymmetrical structure with respect to a first center portion CP1 (or awidthwise-direction center line) of piezoelectric composite layer 310parallel to the first direction X. Each of the plurality ofpiezoelectric portions 311 according to an example embodiment may have asize that increases in a direction from ends EP1 and EP2 to the firstcenter portion CP1 of piezoelectric composite layer 310 in the firstdirection X. Therefore, the plurality of piezoelectric portions 311 mayhave various vibration frequencies corresponding to various sizes (orsize gradients).

Each of the plurality of piezoelectric portions 311 may vibrate in avibration mode of a d31 displacement (or direction). For example, avibration frequency of each of the piezoelectric portions 311 may beinversely proportional to weight (or mass), and thus, may increase ordecrease based on weight or based on a length of a correspondingpiezoelectric portion 311. For example, when a length of eachpiezoelectric portion 311 decreases, the vibration frequency of eachpiezoelectric portion 311 may increase due to the reduction in weight.When a length of each piezoelectric portion 311 increases, the vibrationfrequency of each piezoelectric portion 311 may decrease due to theincrease in weight.

In another example embodiment, a resonance frequency of eachpiezoelectric portion 311 may be adjusted based on a length or stiffnessand may increase or decrease based on a length. For example, when alength of each piezoelectric portion 311 decreases, a primary resonancefrequency of each piezoelectric portion 311 may increase due to thereduction in length, and when a length of each piezoelectric portion 311increases, the primary resonance frequency of each piezoelectric portion311 may decrease due to the increase in length. For example, when alength L of each piezoelectric portion 311 is 50 mm, a wavelength (λ) is100 nm, and a sound wave velocity (ν) is 1,000 m/s, primary resonancefrequency (f₁=ν/λ) (λ=2 L) of each piezoelectric portion 311 may beabout 10 kHz, and when the length L of each piezoelectric portion 311decreases to 25 mm, a primary resonance frequency (f₁) of eachpiezoelectric portion 311 may increase to about 20 kHz.

Because each of the plurality of piezoelectric portions 311 according toan example embodiment has a size that increases in a direction from endsEP1 and EP2 to the first center portion CP1 of piezoelectric compositelayer 310, piezoelectric composite layer 310 according to an exampleembodiment may have various vibration frequencies. As a result, a soundpressure planarization (or flatness) characteristic and a sound pressurecharacteristic of a sound generated based on a vibration of displaypanel 100 may increase and a sound reproduction band may expand.

In some example embodiments, piezoelectric composite layer 310 mayinclude first to N^(th) (where N is an odd number equal to or more thanfive) piezoelectric portions 311[1] to 311[N]. The i+1^(th) (where i is(N−1)/2) piezoelectric portion 311[i+1] may be in the first centerportion CP1 of piezoelectric composite layer 310. The first to i^(th)piezoelectric portions 311[1] to 311[i] may be disposed on a first sideS1 between the one end EP1 and the first center portion CP1 ofpiezoelectric composite layer 310. The i+2^(th) to N^(th) piezoelectricportions 311[i+2] to 311[N] may be disposed on a second side S2 betweenthe other end EP2 opposite to the one end EP1 and the first centerportion CP1 of piezoelectric composite layer 310. Piezoelectricportions, other than the i+1^(th) piezoelectric portion 311[i+1], of thefirst to N^(th) piezoelectric portions 311[1] to 311[N] may have avertical asymmetrical structure with respect to a second center portionCP2 (or a lengthwise direction center line) of piezoelectric compositelayer 310 parallel to the second direction Y. As a result, one end ofthe piezoelectric portions, other than the i+1^(th) piezoelectricportion 311[i+1], of the first to N^(th) piezoelectric portions 311[1]to 311[N], may be spaced apart from one side (or an upper side) ofpiezoelectric composite layer 310 parallel to the first direction X.

According to an example embodiment, the first to N^(th) piezoelectricportions 311 may have the same width W1 and thickness H1 (or height)within a process error range (or an allowable error range or atolerance) occurring in a manufacturing process. The i+1^(th)piezoelectric portion 311[i+1] may have a largest length among lengthsof the piezoelectric portions 311, and for example, may have a firstlength L1 corresponding to a lengthwise length of piezoelectriccomposite layer 310 parallel to the second direction Y. Each of thefirst piezoelectric portion 311[1] and the N^(th) piezoelectric portion311[N] may be disposed closest to an end of piezoelectric compositelayer 310 and may have a smallest length among lengths of thepiezoelectric portions 311, and for example, may have a second length L2that is shorter than the first length L1 of the i+1^(th) piezoelectricportion 311[i+1].

The second to i^(th) piezoelectric portions 311[2] to 311[i] may havedifferent lengths within a range that is longer than the firstpiezoelectric portion 311[1] and shorter than the i+1^(th) piezoelectricportion 311[i+1] and may have a longer length as being closer to thei+1^(th) piezoelectric portion 311[i+1]. The i+2^(th) to N−1^(th)piezoelectric portions 311[i+2] to 311[N−1] may have different lengthswithin a range that is longer than the N^(th) piezoelectric portion311[N] and is shorter than the i+1^(th) piezoelectric portion 311[i+1]and may have a longer length as being closer to the i+1^(th)piezoelectric portion 311[i+1]. Therefore, the first to i+1^(th)piezoelectric portions 311[1] to 311[i+1] may have different vibrationfrequencies, based on different sizes (or lengths), and the i+2^(th) toN^(th) piezoelectric portions 311[i+2] to 311[N] may have differentvibration frequencies, based on different sizes (or lengths).Piezoelectric portions having a horizontal symmetrical structure withrespect to the i+1^(th) piezoelectric portion 311[i+1] of the first toN^(th) piezoelectric portions 311[1] to 311[N] may have the samevibration frequencies.

The plurality of piezoelectric portions 311 according to an exampleembodiment may be grouped into a plurality of groups (or piezoelectricgroups). The plurality of groups may include a same or different numberof piezoelectric portions 311. Piezoelectric portions 311 in the samegroup may have the same size within a process error range (or anallowable error range or a tolerance) occurring in a manufacturingprocess. The plurality of piezoelectric portions 311 may have differentsizes by units of groups. For example, the plurality of piezoelectricportions 311 may have the same width and thickness (or height) withinthe process error range (or the allowable error range or a tolerance)occurring in the manufacturing process and may have different lengths byunits of groups. Accordingly, the plurality of groups may have differentvibration frequencies.

According to an example embodiment, each of the plurality of groups mayinclude two or more of the plurality of piezoelectric portions 311. Twoor more piezoelectric portions 311 in each group may be disposedadjacent to each other or may be in a horizontal symmetrical structurewith respect to the first center portion CP1 of piezoelectric compositelayer 310. Piezoelectric portions in groups other than a group in thefirst center portion CP1 of piezoelectric composite layer 310 may be ina vertical asymmetrical structure with respect to the second centerportion CP2 of piezoelectric composite layer 310.

For example, as in FIG. 3, when piezoelectric composite layer 310includes first to seventeenth piezoelectric portion 311[1] to 311[N],seventeen piezoelectric portion 311[1] to 311[N] may be grouped intofirst to ninth groups. The first group may include one piezoelectricportion in the first center portion CP1 of piezoelectric composite layer310, each of the second to ninth groups may include two piezoelectricportions, and two piezoelectric portions in each of the second to ninthgroups may be in a horizontal symmetrical structure with respect to thefirst center portion CP1 of piezoelectric composite layer 310. Forexample, the first group may include a ninth piezoelectric portion311[i+1] in the first center portion CP1 of piezoelectric compositelayer 310, the second group may include an eighth piezoelectric portion311[i] and a tenth piezoelectric portion 311[i+2] that are closest tothe first group, and the ninth group may include a first piezoelectricportion 311[1] closest to the one end EP1 of piezoelectric compositelayer 310 and a seventeenth piezoelectric portion 311[N] closest to theother end EP2 of piezoelectric composite layer 310. Accordingly, thefirst to ninth groups may have different vibration frequencies due topiezoelectric portions 311 having different sizes, respectively, andvibration frequencies of the groups may be horizontally symmetrical withrespect to the first center portion CP1 of piezoelectric composite layer310.

Each of the plurality of piezoelectric portions 311 according to anexample embodiment may include an inorganic material or a piezoelectricmaterial that each vibrates based on a piezoelectric effect (or apiezoelectric characteristic) caused by an electric field. For example,each of the plurality of piezoelectric portions 311 may be referred toas an active portion, an inorganic material portion, a piezoelectricmaterial portion, or a vibration portion.

Each of the plurality of piezoelectric portions 311 may be formed of aceramic-based material for generating a relatively high vibration, ormay be formed of piezoelectric ceramic having a perovskite-basedcrystalline structure. For example, the inorganic material portion ineach of the plurality of piezoelectric portions 311 may include one ormore materials of lead (Pb), zirconium (Zr), titanium (Ti), zinc (Zn),nickel (Ni), manganese (Mn) and niobium (Nb). In another exampleembodiment, the inorganic material portion in each of the plurality ofpiezoelectric portions 311 may include a lead zirconate titanate(PZT)-based material including lead (Pb), zirconium (Zr), and titanium(Ti) or may include a lead zirconate nickel niobate (PZNN)-basedmaterial including lead (Pb), zinc (Zn), nickel (Ni), and niobium (Nb).The inorganic material portion may include at least one of CaTiO₃,BaTiO₃, and SrTiO₃ each without Pb. The plurality of piezoelectricportions 311 having such a configuration may alternately contract andexpand based on an inverse piezoelectric effect based on a signalapplied thereto. As a result, the plurality of piezoelectric portions311 may vibrate based on a vibration mode (or a bending phenomenon) ofthe d31 displacement.

The flexible portion 313 may provide flexibility to piezoelectriccomposite layer 310 and may form a whole shape of piezoelectriccomposite layer 310. Flexible portion 313 according to an exampleembodiment may be disposed between the plurality of piezoelectricportions 311 and may be connected to a piezoelectric portion 311adjacent thereto to allow piezoelectric composite layer 310 to havevarious shapes. For example, flexible portion 313 may surround or coverat least three or four outer surfaces (or sidewalls) of each of theplurality of piezoelectric portions 311.

The flexible portion 313 according to an example embodiment may havemodulus and viscoelasticity that are lower than those of eachpiezoelectric portion 311. This may enhance the reliability of eachpiezoelectric portion 311 vulnerable to an impact due to a brittlenesscharacteristic. For example, when flexible vibration module 300 forvibrating display panel 100 has an impact resistance and high stiffness,flexible vibration module 300 may have a maximum vibrationcharacteristic. In order for flexible vibration module 300 to have animpact resistance and high stiffness, flexible portion 313 may include amaterial having a relatively high damping factor (tan δ) and relativelyhigh stiffness. For example, flexible portion 313 may include a materialhaving a damping factor (tan δ) of about 0.1 Gpa to about 1 Gpa andrelatively high stiffness of about 0 Gpa to about 10 Gpa. A dampingfactor (tan δ) and a stiff characteristic may be described based on acorrelation between a loss coefficient and modulus. Flexible portion 313may include a material having a loss coefficient of about 0.01 to about1 and modulus of about 1 Gpa to about 10 Gpa.

Flexible portion 313 may include an organic material or an organicpolymer that each has a flexible characteristic in comparison withpiezoelectric portions 311. For example, flexible portion 313 mayinclude an organic material, an organic polymer, an organicpiezoelectric material, or an organic non-piezoelectric material. Forexample, the flexible portion 313 may be referred to as an organicmaterial portion, an adhesive portion, an elastic portion, a bendingportion, or a damping portion. Flexible portion 313 according to anexample embodiment may include at least one of an organic piezoelectricmaterial and an organic non-piezoelectric material. As a result,flexible portion 313 may absorb an impact applied to the piezoelectricportions 313, thereby enhancing the total durability of flexiblevibration module 300. The organic piezoelectric material included in theflexible portion 313 may be an organic material having an electroactivecharacteristic. For example, the organic piezoelectric material mayinclude at least one of polyvinylidene fluoride (PVDF), β-Polyvinylidenefluoride (β-PVDF), polyvinylidene-trifluoroethylene (PVDF-TrFE), andpolyvinylidene-trifluoroethylene-chloro fluoro ethelene (PVDF-TrFE-CFE).

An organic non-piezoelectric material in flexible portion 313 mayinclude a curable resin composition and an adhesive including thecurable resin composition. For example, the organic non-piezoelectricmaterial may include at least one of an epoxy-based polymer, anacryl-based polymer, and a silicon-based polymer. Flexible portion 313according to an example embodiment may include a plurality of flexiblepatterns 313 a and a flexible dummy pattern 313 b.

Each of the plurality of flexible patterns 313 a may be configured tofill a gap region between the plurality of piezoelectric portions 311 ofpiezoelectric composite layer 310. For example, the plurality offlexible patterns 313 a may each be disposed between two adjacentpiezoelectric portions of the plurality of piezoelectric portions 311that are parallel to the second direction Y and are spaced apart fromone another by a certain interval or distance in the first direction X.Therefore, each may be a line pattern having a second width W2corresponding to an interval or distance between the plurality ofpiezoelectric portions 311.

According to an example embodiment, the plurality of flexible patterns313 a may each have the same second width W2 within a process errorrange (or an allowable error range or a tolerance) occurring in amanufacturing process. The second width W2 of each of the plurality offlexible patterns 313 a may be the same as or different from the firstwidth W1 of each piezoelectric portion 311. A size of each of theplurality of flexible patterns 313 a may be adjusted based on a neededcondition of at least one of a vibration characteristic, flexibility,and a size of flexible vibration module 300. For example, in the displayapparatus or flexible vibration module 300 having a piezoelectriccharacteristic rather than flexibility, the first width W1 of eachpiezoelectric portion 311 may be adjusted to be greater than the secondwidth W2 of each of the plurality of flexible patterns 313 a.

In another example embodiment, in the display apparatus or flexiblevibration module 300 having flexibility rather than a piezoelectriccharacteristic, the first width W1 of each piezoelectric portion 311 maybe adjusted to be less than the second width W2 of each of the pluralityof flexible patterns 313 a. Accordingly, a size of piezoelectriccomposite layer 310 may be adjusted based on a characteristic needed forthe display apparatus, thus it may be easy to design piezoelectriccomposite layer 310.

Flexible dummy pattern 313 b may be in a dummy region where theplurality of flexible patterns 313 a and the plurality of piezoelectricportions 311 in piezoelectric composite layer 310 are not disposed.Flexible dummy pattern 313 b may form a shape, other than a shape wherethe piezoelectric portions 311 and the flexible patterns 313 a aredisposed, of a whole shape of flexible vibration module 300.

Flexible dummy pattern 313 b according to an example embodiment may beconfigured to fill a dummy region (or a region where a piezoelectricportion is not disposed) occurring in a corner of each of a first sideS1 and a second side S2 of piezoelectric composite layer 310, based on alength gradient of each of the plurality of piezoelectric portions 311.Flexible dummy pattern 313 b may be connected to one side surface ofeach of the plurality of flexible patterns 313 a. For example, each ofthe plurality of flexible patterns 313 a may have a finger structurethat extends from flexible dummy pattern 313 b to a space between theplurality of piezoelectric portions 311.

In some example embodiments, piezoelectric composite layer 310 may havea tetragonal shape, based on the plurality of piezoelectric portions311, the plurality of flexible patterns 313 a, and the flexible dummypattern 313 b each being disposed in the same plane. In other exampleembodiments, piezoelectric composite layer 310 may have a circularshape, an elliptical shape, a triangular shape, or a five ormore-angular polygonal shape. For example, piezoelectric composite layer310 may have a five or more-angular polygonal shape, and piezoelectriccomposite layer 310 may be a vibration source (or a vibrator or avibration body) that is approximately circular in shape, therebyenhancing a vibration characteristic.

In piezoelectric composite layer 310, piezoelectric portions 311 andflexible patterns 313 a of flexible portion 313 may be alternatelyrepeated and connected to one another, thus piezoelectric compositelayer 310 may have a thin film type. Therefore, piezoelectric compositelayer 310 may be bent based on a shape of display panel 100 and may havea size corresponding to display panel 100 or may have a size forrealizing a vibration characteristic or a sound characteristic that iseach adjusted based on a vibration of display panel 100.

First electrode layer 320 may be disposed on a first surface (or a rearsurface) of piezoelectric composite layer 310 and may be electricallyconnected to a first surface of each of the plurality of piezoelectricportions 311. First electrode layer 320 according to an exampleembodiment may include a transparent conductive material, asemitransparent conductive material, or an opaque conductive material.For example, examples of the transparent conductive material or thesemitransparent conductive material may include indium tin oxide (ITO)or indium zinc oxide (IZO). Examples of the opaque conductive materialmay include aluminum (Al), copper (Cu), gold (Au), silver (Ag),molybdenum (Mo), and magnesium (Mg) or an alloy thereof

Second electrode layer 330 may be disposed on a second surface (or afront surface), which is opposite to the first surface, of piezoelectriccomposite layer 310 and may be electrically connected to a secondsurface of each of the plurality of piezoelectric portions 311. Secondelectrode layer 330 according to an example embodiment may include atransparent conductive material, a semitransparent conductive material,or an opaque conductive material. For example, second electrode layer330 may include the same material as that of first electrode layer 320.

Piezoelectric composite layer 310 may be polarized by a certain voltageapplied to first electrode layer 320 and second electrode layer 330 in acertain temperature atmosphere or a temperature atmosphere that ischanged from a high temperature to a room temperature. A polarizationdirection of each of the plurality of piezoelectric portions 311 may beadjusted based on a voltage applied to first electrode layer 320 andsecond electrode layer 330.

Flexible vibration module 300 according to an example embodiment of thepresent disclosure may further include a first protection film 340 and asecond protection film 350. First protection film 340 may be on thefirst electrode layer 320 and may protect the first surface ofpiezoelectric composite layer 310 or the first electrode layer 320. Forexample, the first protection film 340 may be a polyimide (PI) film or apolyethyleneterephthalate (PET) film. Second protection film 350 may beon second electrode layer 330 and may protect the second surface ofpiezoelectric composite layer 310 or second electrode layer 330. Forexample, second protection film 350 may be a polyimide (PI) film or apolyethyleneterephthalate (PET) film.

In another example embodiment, in flexible vibration module 300, anarrangement structure of piezoelectric portions 311 is not limited tothe arrangement structure illustrated in FIG. 3. The arrangementstructure may be changed to various structures, based on a neededcondition of at least one of a vibration characteristic, flexibility,and a size of flexible vibration module 300. For example, a lengthgradient or a vibration frequency of each of piezoelectric portions 311may not be adjusted to progressively increase in a direction from endsEP1 and EP2 to the first center portion CP1 of piezoelectric compositelayer 310. In other example embodiments, a length gradient or avibration frequency of each of piezoelectric portions 311 may beadjusted to be randomly changed, or may be adjusted to progressivelyincrease in a direction from end EP1 to end EP2 of piezoelectriccomposite layer 310.

Flexible vibration module 300 according to the first example embodimentof the present disclosure may vibrate based on bending caused by aninverse piezoelectric effect based on a signal applied to each of theplurality of piezoelectric portions 311 to vibrate display panel 100,thereby providing a user with a sound or a haptic feedback. Flexibleportion 313 filled or disposed between the plurality of piezoelectricportions 311 may have flexibility. Therefore, even when piezoelectriccomposite layer 310 bends, piezoelectric portions 311 may not be damagedor may not be reduced in performance.

Flexible vibration module 300 according to the first example embodimentof the present disclosure may be disposed on the rear surface of displaypanel 100 to sufficiently vibrate display panel 100 in a verticaldirection (or a forward-backward direction), thereby outputting adesired sound to a forward region in front of the display apparatus.Piezoelectric portions 311 and flexible portion 313 may each configurepiezoelectric composite layer 310 to be implemented in a pattern shape.As a result, piezoelectric composite layer 310 may have a sizecorresponding to display panel 100, whereby panel coverage (or a contactarea) of flexible vibration module 300 contacting display panel 100 mayincrease to enhance a sound characteristic based on a vibration ofdisplay panel 100. For example, flexible vibration module 300 may beconfigured to have a wide area corresponding to the same size as that ofdisplay panel 100. As a result, a sound pressure characteristic of alow-pitched sound band which is a drawback of a film type piezoelectricmay be improved and the driving voltage may be reduced. Flexiblevibration module 300 according to an example embodiment of the presentdisclosure may include the inorganic material portion and the organicmaterial portion and may be a thin film type. Therefore, flexiblevibration module 300 may be integrated into or equipped in the displayapparatus without interference caused by a mechanical element and/oranother element configuring the display apparatus.

Flexible vibration module 300 according to the first example embodimentof the present disclosure may have various vibration frequencies basedon a size gradient of each of the plurality of piezoelectric portions311. Therefore, flexible vibration module 300 may vibrate display panel100 by using a vibration having various vibration frequencies with anelectric field based on a signal applied to each of the plurality ofpiezoelectric portions 311. Accordingly, a sound pressure planarization(or flatness) characteristic and a sound pressure characteristic of asound generated based on a vibration of display panel 100 may increaseand a sound reproduction band may expand.

FIG. 5 illustrates a flexible vibration module 300 according to a secondexample embodiment of the present disclosure and illustrates an exampleembodiment implemented by modifying an arrangement structure of apiezoelectric portion in piezoelectric composite layer illustrated inFIG. 3. As illustrated in FIG. 5, a piezoelectric composite layer 310may include a plurality of piezoelectric portions 311 and a flexibleportion 313 disposed between the plurality of piezoelectric portions311.

The plurality of piezoelectric portions 311 may have a horizontalsymmetrical structure with respect to a first center portion CP1 ofpiezoelectric composite layer 310 parallel to a first direction X. Eachof the plurality of piezoelectric portions 311 may have a size thatprogressively decreases in a direction from ends EP1 and EP2 to thefirst center portion CP1 of piezoelectric composite layer 310 in thefirst direction X, and thus, may have various vibration frequenciescorresponding to various sizes (or a length gradient). However, each ofthe plurality of piezoelectric portions 311 progressively decreases in adirection from ends EP1 and EP2 to the first center portion CP1 ofpiezoelectric composite layer 310.

Flexible portion 313 may provide flexibility to piezoelectric compositelayer 310 and may form a whole shape of piezoelectric composite layer310. Flexible portion 313 according to an example embodiment may bedisposed between the plurality of piezoelectric portions 311 and may beconnected to a piezoelectric portion 311 adjacent thereto to allowpiezoelectric composite layer 310 to have various shapes. For example,flexible portion 313 may surround or cover at least three or four outersurfaces (or sidewalls) of each of the plurality of piezoelectricportions 311. Flexible portion 313 may include a plurality of flexiblepatterns 313 a each configured to fill a gap region between theplurality of piezoelectric portions 311 and a flexible dummy pattern 313b in a dummy region where the plurality of piezoelectric portions 311and the plurality of flexible patterns 313 a are not disposed. Exceptfor an arrangement position of the flexible portion illustrated in eachof FIGS. 3 and 4, the flexible portion 313 is the same as the flexibleportion illustrated in each of FIGS. 3 and 4.

Flexible vibration module 300 according to the second example embodimentof the present disclosure may vibrate display panel 100 at variousvibration frequencies based on a size gradient (or a length gradient) ofeach of the plurality of piezoelectric portions 311. As a result, asound pressure planarization (or flatness) characteristic and a soundpressure characteristic of a sound generated based on the vibration ofdisplay panel 100 may increase and a sound reproduction band may expand.For example, in flexible vibration module 300 according to the secondexample embodiment of the present disclosure, piezoelectric portions311, which have a relatively low vibration frequency (or a low resonancefrequency) due to a relatively large size, may be adjacent to ends EP1and EP2 of each of piezoelectric portions 311. As a result, a vibrationarea of display panel 100 vibrating by piezoelectric portions 311 mayexpand, thus a sound of a low-pitched sound band may be improved.Accordingly, a vibration area of display panel 100 generating asufficient low-pitched sound band may be used as broad as possible.

FIG. 6 illustrates a flexible vibration module 300 according to a thirdexample embodiment of the present disclosure and illustrates an exampleembodiment implemented by modifying an arrangement structure of apiezoelectric portion in the piezoelectric composite layer illustratedin FIG. 3. As illustrated in FIG. 6, in flexible vibration module 300according to the third example embodiment of the present disclosure, apiezoelectric composite layer 310 may include a plurality ofpiezoelectric portions 311 and a flexible portion 313 between theplurality of piezoelectric portions 311. Each of the plurality ofpiezoelectric portions 311 may have a size that progressively increasesin a direction from ends EP1 and EP2 to a first center portion CP1 ofpiezoelectric composite layer 310 in a first direction X, and thus, mayhave various vibration frequencies corresponding to various sizes.

A lengthwise direction center portion of each of the plurality ofpiezoelectric portions 311 parallel to a second direction Y may be in asecond center portion CP2 of piezoelectric composite layer 310. Bothends of the piezoelectric portions other than a piezoelectric portion inthe first center portion CP1 of piezoelectric composite layer 310 may bespaced apart from both sides (or an upper side and a lower side) ofpiezoelectric composite layer 310 parallel to the first direction X.Each of the plurality of piezoelectric portions 311 may have a size thatprogressively increases in a direction from ends EP1 and EP2 to thefirst center portion CP1 of piezoelectric composite layer 310 in thefirst direction X, and thus, may have various vibration frequenciescorresponding to various sizes (or a length gradient). Except for theplurality of piezoelectric portions 311 being in a horizontalsymmetrical structure with respect to the first center portion CP1 ofpiezoelectric composite layer 310 and in a vertical symmetricalstructure with respect to the second center portion CP2 of piezoelectriccomposite layer 310, the plurality of piezoelectric portions 311 are thesame as FIGS. 3 and 4.

Flexible portion 313 may provide flexibility to piezoelectric compositelayer 310 and may form a whole shape of piezoelectric composite layer310. Flexible portion 313 according to an example embodiment may bebetween the plurality of piezoelectric portions 311 and may be connectedto a piezoelectric portion 311 adjacent thereto to allow piezoelectriccomposite layer 310 to have various shapes. For example, flexibleportion 313 may surround or cover all of four outer surfaces (orsidewalls) of each of the plurality of piezoelectric portions 311. Theflexible portion 313 may include a plurality of flexible patterns 313 aeach configured to fill a gap region between the plurality ofpiezoelectric portions 311 and a flexible dummy pattern 313 b in a dummyregion where the plurality of piezoelectric portions 311 and theplurality of flexible patterns 313 a are not disposed. Except for anarrangement position of the flexible portion illustrated in each ofFIGS. 3 and 4, the flexible portion 313 is the same as the flexibleportion illustrated in each of FIGS. 3 and 4. In flexible vibrationmodule 300 according to the present example embodiment, each of theplurality of piezoelectric portions 311 may have a size thatprogressively decreases in a direction from ends EP1 and EP2 to thefirst center portion CP1 of piezoelectric composite layer 310 in thefirst direction X.

In flexible vibration module 300 according to the third exampleembodiment, an arrangement structure of the piezoelectric portions 311is not limited to the arrangement structure illustrated in FIG. 6. Inthis example embodiment, flexible vibration module 300 may be changed tovarious structures, based on a needed condition of at least one of avibration characteristic, flexibility, and a size of flexible vibrationmodule 300. For example, a length gradient or a vibration frequency ofeach of the piezoelectric portions 311 may not be adjusted to increaseprogressively in a direction from ends EP1 and EP2 to the first centerportion CP1 of piezoelectric composite layer 310 and may be adjusted tobe randomly changed, or may be adjusted to increase progressively in adirection from end EP1 to end EP2 of piezoelectric composite layer 310or to be randomly changed.

FIG. 7 illustrates a flexible vibration module 300 according to a fourthexample embodiment of the present disclosure, and FIG. 8 is across-sectional view taken along line illustrated in FIG. 7. FIGS. 7 and8 illustrate an example embodiment implemented by modifying a structureof the piezoelectric composite layer illustrated in FIG. 3. Asillustrated in FIGS. 7 and 8, flexible vibration module 300 according tothe fourth example embodiment of the present disclosure, a piezoelectriccomposite layer 310 may include a plurality of piezoelectric portions311 and a flexible portion 313 between the plurality of piezoelectricportions 311. The plurality of piezoelectric portions 311 may include apolygonal pattern. For example, the plurality of piezoelectric portions311 may have a line pattern having a certain first length L1, may bespaced apart from one another in a first direction X, and may be inparallel in a second direction Y.

Some of the plurality of piezoelectric portions 311 according to anexample embodiment may have a different size. A size of each of theplurality of piezoelectric portions 311 may be defined as one of alength, a width, a thickness, a width, an area, and a volume. Forexample, some of the plurality of piezoelectric portions 311 may havethe same size within a process error range (or an allowable error rangeor a tolerance) occurring in a manufacturing process, and the otherpiezoelectric portions 311 may have different sizes, respectively.

The plurality of piezoelectric portions 311 may have a horizontalsymmetrical structure with respect to a first center portion CP1 ofpiezoelectric composite layer 310 and may have a vertical symmetricalstructure with respect to a second center portion CP2 of piezoelectriccomposite layer 310. Each of the plurality of piezoelectric portions 311may have a size that progressively increases in a direction from endsEP1 and EP2 to the first center portion CP1 of piezoelectric compositelayer 310 in the first direction X, and thus, may have various vibrationfrequencies corresponding to various sizes (or a width gradient).

Each of the plurality of piezoelectric portions 311 according to thepresent example embodiment may vibrate in a vibration mode of a d32displacement (or direction). Each of a vibration frequency and aresonance frequency of each of the piezoelectric portions 311 mayincrease as a width thereof decreases in the first direction X.Piezoelectric composite layer 310 according to an example embodiment mayinclude first to N^(th) (where N is an odd number equal to or more thanfive) piezoelectric portions 311[1] to 311[N], and the i+1^(th) (where iis (N−1)/2) piezoelectric portion 311[i+1] may be in the first centerportion CP1 of piezoelectric composite layer 310. The first to i^(th)piezoelectric portions 311[1] to 311[i] may be disposed on a first sideS1 between one end EP1 and the first center portion CP1 of piezoelectriccomposite layer 310. The i+2^(th) to N^(th) piezoelectric portions311[i+2] to 311[N] may be disposed on a second side S2 between the otherend EP2 opposite to the one end EP1 and the first center portion CP1 ofpiezoelectric composite layer 310.

According to an example embodiment, the first to N^(th) piezoelectricportions 311 may have the same length L1 and thickness H1 (or height)within a process error range (or an allowable error range or atolerance) occurring in a manufacturing process. The i+1^(th)piezoelectric portion 311[i+1] may have a widest width W3 among widthsof the piezoelectric portions 311. Each of the first piezoelectricportion 311[1] and the N^(th) piezoelectric portion 311[N] may bedisposed closest to an end of piezoelectric composite layer 310 and mayhave a narrowest width W4 among the widths of the piezoelectric portions311. The second to i^(th) piezoelectric portions 311[2] to 311[i] mayhave different widths within a range that is wider than the firstpiezoelectric portion 311[1] and is narrower than the i+1^(th)piezoelectric portion 311[i+1] and may have a wider width as beingcloser to the i+1^(th) piezoelectric portion 311[i+1]. The i+2^(th) toN−1^(th) piezoelectric portions 311[i+2] to 311[N−1] may have differentwidths within a range that is wider than the N^(th) piezoelectricportion 311[N] and is narrower than the i+1^(th) piezoelectric portion311[i+1] and may have a wider width as being closer to the i+1^(th)piezoelectric portion 311[i+1]. Therefore, the first to i+1^(th)piezoelectric portions 311[1] to 311[i+1] may have different vibrationfrequencies, based on respectively different widths, and the i+2^(th) toN^(th) piezoelectric portions 311[i+2] to 311[N] may have differentvibration frequencies, based on respectively different widths.Piezoelectric portions having a horizontal symmetrical structure withrespect to the i+1^(th) piezoelectric portion 311[i+1] of the first toN^(th) piezoelectric portions 311[1] to 311[N] may have the samevibration frequencies.

The plurality of piezoelectric portions 311 according to an exampleembodiment may be grouped into a plurality of groups (or piezoelectricgroups). The plurality of groups may include a same or respectivelydifferent number of piezoelectric portions 311. Piezoelectric portions311 in the same group may have the same size within a process errorrange (or an allowable error range or a tolerance) occurring in amanufacturing process. The plurality of piezoelectric portions 311 mayhave different sizes by units of groups, respectively. For example, theplurality of piezoelectric portions 311 may have the same width andthickness (or height) within the process error range (or the allowableerror range or a tolerance) occurring in the manufacturing process andmay have different lengths by units of groups, respectively.Accordingly, the plurality of groups may have different vibrationfrequencies, respectively.

According to an example embodiment, each of the plurality of groups mayinclude two or more of the plurality of piezoelectric portions 311, andtwo or more piezoelectric portions 311 in each group may be disposedadjacent to each other or may be in a horizontal symmetrical structurewith respect to the first center portion CP1 of piezoelectric compositelayer 310. For example, as in FIG. 7, when piezoelectric composite layer310 includes first to seventeenth piezoelectric portion 311[1] to311[N], seventeen piezoelectric portion 311[1] to 311[N] may be groupedinto first to ninth groups.

The first group may include one piezoelectric portion 311[i+1] in thefirst center portion CP1 of piezoelectric composite layer 310. Each ofthe second to ninth groups may include two piezoelectric portions. Twopiezoelectric portions in each of the second to ninth groups may be in ahorizontal symmetrical structure with respect to the first centerportion CP1 of piezoelectric composite layer 310. For example, the firstgroup may include a ninth piezoelectric portion 311[i+1] that has awidest width W3 and is in the first center portion CP1 of piezoelectriccomposite layer 310. The second group may include an eighthpiezoelectric portion 311[i] and a tenth piezoelectric portion 311[i+2]that are closest to the first group. The ninth group may include a firstpiezoelectric portion 311[1] closest to the one end EP1 of piezoelectriccomposite layer 310 and a seventeenth piezoelectric portion 311[N]closest to the other end EP2 of piezoelectric composite layer 310. Thefirst and seventeenth piezoelectric portion 311[1] and 311[N] may have anarrowest width W4 among the widths of the piezoelectric portion 311.Accordingly, the first to ninth groups may have different vibrationfrequencies due to piezoelectric portions 311 having different widths,respectively, and vibration frequencies of the groups may behorizontally symmetrical with respect to the first center portion CP1 ofpiezoelectric composite layer 310.

The flexible portion 313 may include a plurality of flexible patterns313 a each between the plurality of piezoelectric portions 311. Theplurality of flexible patterns 313 a may each be between two adjacentpiezoelectric portions of the plurality of piezoelectric portions 311and may improve an impact resistance of the piezoelectric portions 311and may provide flexibility to flexible vibration module 300. Theplurality of flexible patterns 313 a and the plurality of piezoelectricportions 311 may be alternately disposed (or arranged) on the same plane(or the same layer). Each of the plurality of flexible patterns 313 amay be configured to fill a gap between two adjacent piezoelectricportions of the plurality of piezoelectric portions 311 and may beconnected to or attached on a piezoelectric portion 311 adjacentthereto. For example, the plurality of flexible patterns 313 a may havea line pattern having a width W5 corresponding to a gap between twoadjacent piezoelectric portions 311.

The plurality of flexible patterns 313 a may each have the same sizewithin a process error range (or an allowable error range or atolerance) occurring in a manufacturing process, and for example, mayhave a width, an area, or a volume. However, the present exampleembodiment is not limited thereto, and the plurality of flexiblepatterns 313 a may have different sizes or may have a size correspondingto a size of two adjacent piezoelectric portions 311. Therefore, a sizeof each of the plurality of flexible patterns 313 a may be adjustedbased on a needed condition of at least one of a vibrationcharacteristic, flexibility, and a size of flexible vibration module300. For example, in the display apparatus or flexible vibration module300 needing a piezoelectric characteristic rather than flexibility, thewidth W5 of each flexible pattern 313 a may relatively decrease. Inanother example embodiment, in the display apparatus or flexiblevibration module 300 needing flexibility rather than a piezoelectriccharacteristic, the width W5 of each flexible pattern 313 a mayrelatively increase. Accordingly, a size of piezoelectric compositelayer 310 may be adjusted based on a characteristic needed for thedisplay apparatus, and thus, it may be easy to design piezoelectriccomposite layer 310.

In flexible vibration module 300 according to the present exampleembodiment, the plurality of piezoelectric portions 311 may have ahorizontal symmetrical structure with respect to a first center portionCP1 of piezoelectric composite layer 310, have a vertical symmetricalstructure with respect to a second center portion CP2 of piezoelectriccomposite layer 310, and each have a size that decreases progressivelyin a direction from ends EP1 and EP2 to the first center portion CP1 ofpiezoelectric composite layer 310 in the first direction X. As a result,the plurality of piezoelectric portions 311 may have various vibrationfrequencies corresponding to various sizes (or a width gradient).

In flexible vibration module 300 according to the fourth exampleembodiment, an arrangement structure of the piezoelectric portions 311is not limited to the arrangement structure illustrated in FIG. 7 andmay be changed to various structures, based on a needed condition of atleast one of a vibration characteristic, flexibility, and a size offlexible vibration module 300. For example, a width gradient or avibration frequency of each of the piezoelectric portions 311 may not beadjusted to increase progressively in a direction from ends EP1 and EP2to the first center portion CP1 of piezoelectric composite layer 310 andmay be adjusted to be randomly changed, or may be adjusted to increaseprogressively in a direction from end EP1 to end EP2 of piezoelectriccomposite layer 310 or to be randomly changed.

FIG. 9 illustrates a flexible vibration module 300 according to a fifthexample embodiment of the present disclosure, and FIG. 10 is across-sectional view taken along line IV-IV′ illustrated in FIG. 9.FIGS. 9 and 10 illustrate an example embodiment implemented by modifyinga structure of the piezoelectric composite layer illustrated in FIG. 3.As illustrated in FIGS. 9 and 10, flexible vibration module 300according to the fifth example embodiment of the present disclosure, apiezoelectric composite layer 310 may include a plurality ofpiezoelectric portions 311 and a flexible portion 313 between theplurality of piezoelectric portions 311.

The plurality of piezoelectric portions 311 may include a polygonalpattern. For example, the plurality of piezoelectric portions 311 mayhave a line pattern having a certain length, may be spaced apart fromone another in a first direction X, and may be in parallel in a seconddirection Y. The plurality of piezoelectric portions 311 according to anexample embodiment may each have the same size within a process errorrange (or an allowable error range or a tolerance) occurring in amanufacturing process. For example, the plurality of piezoelectricportions 311 may each have the same width W6, thickness, and length.Sizes of the plurality of the piezoelectric portions 311 may behorizontally symmetrical with respect to a first center portion CP1 (ora widthwise direction center line) of piezoelectric composite layer 310parallel to a first direction X.

The plurality of piezoelectric portions 311 may each include a lowerpiezoelectric portion 311 a and an upper piezoelectric portion 311 b.Thicknesses (or heights) of the lower piezoelectric portion 311 a andthe upper piezoelectric portion 311 b of each of the plurality ofpiezoelectric portions 311 may all differ. The thickness (or heights) ofthe lower piezoelectric portion 311 a and the upper piezoelectricportion 311 b may have different thickness ratios (or a thicknessgradient) by units of the piezoelectric portion 311. Such a thicknessratio may be horizontally symmetrical with respect to the first centerportion CP1 of piezoelectric composite layer 310. For example, the lowerpiezoelectric portion 311 a and the upper piezoelectric portion 311 beach in each piezoelectric portion 311 may have an asymmetricalthickness with respect to a center thickness (or a center height).

In another example embodiment, some of the plurality of piezoelectricportions 311 may each include a lower piezoelectric portion 311 a and anupper piezoelectric portion 311 b each having the same thickness (orheight), and the other piezoelectric portions 311 may each include alower piezoelectric portion 311 a and an upper piezoelectric portion 311b each having different thicknesses (or heights). For example, withrespect to the first direction X, one piezoelectric portion 311[#5]disposed between the one end EP1 and the first center portion CP1 ofpiezoelectric composite layer 310 may include a lower piezoelectricportion 311 a and an upper piezoelectric portion 311 b each having thesame thickness (or height). One piezoelectric portion 311[#13] disposedbetween the other end EP2 and the first center portion CP1 ofpiezoelectric composite layer 310 may include a lower piezoelectricportion 311 a and an upper piezoelectric portion 311 b may each have thesame thickness (or height). Except for the piezoelectric portions311[#5] and 311[#13] including a lower piezoelectric portion 311 a andan upper piezoelectric portion 311 b each having the same thickness (orheight), the other piezoelectric portions may each include a lowerpiezoelectric portion 311 a and an upper piezoelectric portion 311 beach having different thicknesses (or heights).

The lower piezoelectric portion 311 a of each of the plurality ofpiezoelectric portions 311 may have a partial thickness of a totalthickness of a corresponding piezoelectric portion 311. At least one ofa plurality of lower piezoelectric portions 311 a may have a differentthickness. For example, some of plurality of lower piezoelectricportions 311 a may have the same thickness within a process error range(or an allowable error range or a tolerance) occurring in amanufacturing process, and the other lower piezoelectric portions 311 amay each have different thicknesses. In another example embodiment, theplurality of lower piezoelectric portions 311 a may each have differentthicknesses.

The plurality of lower piezoelectric portions 311 a may have ahorizontal symmetrical structure with respect to the first centerportion CP1 of piezoelectric composite layer 310. For example, theplurality of lower piezoelectric portions 311 a may be in a steppedshape between ends EP1 and EP2 and the first center portion CP1 ofpiezoelectric composite layer 310. Each of the plurality of lowerpiezoelectric portions 311 a may have a thickness that progressivelydecreases in a direction from ends EP1 and EP2 to the first centerportion CP1 of piezoelectric composite layer 310. As a result, theplurality of lower piezoelectric portions 311 a may each have variousvibration frequencies or different vibration frequencies eachcorresponding to various sizes (or a thickness gradient).

At least two of the upper piezoelectric portions 311 b of the pluralityof piezoelectric portions 311 may have a different vibration frequency.For example, the upper piezoelectric portions 311 b of the plurality ofpiezoelectric portions 311 may each have different vibrationfrequencies.

The upper piezoelectric portion 311 b of each of the plurality ofpiezoelectric portions 311 may have a thickness obtained by subtractinga thickness of an overlapping lower piezoelectric portion 311 a from atotal thickness of a corresponding piezoelectric portion 311. Except fora piezoelectric portion in the first center portion CP1 of piezoelectriccomposite layer 310, the other piezoelectric portions may have anasymmetrical thickness structure with respect to a center thickness (ora center height) of the piezoelectric portion 311. For example, theplurality of upper piezoelectric portions 311 b may be in a steppedshape between ends EP1 and EP2 and the first center portion CP1 ofpiezoelectric composite layer 310. Each of the plurality of upperpiezoelectric portions 311 b may have a thickness that progressivelyincreases in a direction from ends EP1 and EP2 to the first centerportion CP1 of piezoelectric composite layer 310. As a result, theplurality of lower piezoelectric portions 311 a may have variousvibration frequencies corresponding to various sizes (or a thicknessgradient).

Except for the piezoelectric portions 311[#5] and 311[#13] including alower piezoelectric portion 311 a and an upper piezoelectric portion 311b each having the same thickness (or height), the other piezoelectricportions may have a vertical stacked structure. The vertically stackedstructure may include a lower piezoelectric portion 311 a having arelatively thick thickness and an upper piezoelectric portion 311 bhaving a relatively thin thickness. Alternatively the vertically stackedstructure may include a lower piezoelectric portion 311 a having arelatively thin thickness and an upper piezoelectric portion 311 bhaving a relatively thick thickness, based on an arrangement positionbetween ends EP1 and EP2 and the first center portion CP1 ofpiezoelectric composite layer 310.

Each of the plurality of lower piezoelectric portions 311 a and each ofthe plurality of upper piezoelectric portions 311 b according to thepresent example embodiment may vibrate in a vibration mode of a d33displacement (or direction). Each of a vibration frequency and aresonance frequency of each of the piezoelectric portions 311 mayincrease as a thickness (or height) decreases in a third direction Z (ora thickness direction).

The plurality of piezoelectric portions 311 according to an exampleembodiment may be grouped into a plurality of groups (or piezoelectricgroups). The plurality of groups may include a same or respectivelydifferent number of piezoelectric portions 311. For example, a lowerpiezoelectric portion 311 a and an upper piezoelectric portion 311 b ofeach of the plurality of piezoelectric portions 311 may have the samelength and width within a process error range (or an allowable errorrange or a tolerance) occurring in a manufacturing process and may eachhave different sizes by units of groups. Accordingly, the plurality ofgroups may each have different vibration frequencies.

According to an example embodiment, each of the plurality of groups mayinclude two or more of the plurality of piezoelectric portions 311. Twoor more piezoelectric portions 311 in each group may be disposedadjacent to each other or may be in a horizontal symmetrical structurewith respect to the first center portion CP1 of piezoelectric compositelayer 310. For example, as in FIGS. 9 and 10, when piezoelectriccomposite layer 310 includes first to seventeenth piezoelectric portion311, seventeen piezoelectric portion 311 may be grouped into first toninth groups.

The first group may include one piezoelectric portion 311[#9] in thefirst center portion CP1 of piezoelectric composite layer 310. Each ofthe second to ninth groups may include two piezoelectric portions, andtwo piezoelectric portions in each of the second to ninth groups may bein a horizontal symmetrical structure with respect to the first centerportion CP1 of piezoelectric composite layer 310. For example, the firstgroup may include a ninth piezoelectric portion 311[#9] in the firstcenter portion CP1 of piezoelectric composite layer 310. The secondgroup may include an eighth piezoelectric portion and a tenthpiezoelectric portion that are closest to the first group, and the ninthgroup may include a first piezoelectric portion closest to the one endEP1 of piezoelectric composite layer 310 and a seventeenth piezoelectricportion closest to the other end EP2 of piezoelectric composite layer310. Piezoelectric portions 311[#5] to 311[#13] in some groups of thesecond to ninth groups may each include a lower piezoelectric portion311 a and an upper piezoelectric portion 311 b each having the samethickness. Piezoelectric portions in the other groups may each include alower piezoelectric portion 311 a and an upper piezoelectric portion 311b each having different thicknesses by units of groups, based on anarrangement position. Accordingly, the first to ninth groups may havedifferent vibration frequencies due to a piezoelectric portion 311including a lower piezoelectric portion 311 a and an upper piezoelectricportion 311 b each having different sizes by units of groups, andvibration frequencies of the groups may be horizontally symmetrical withrespect to the first center portion CP1 of piezoelectric composite layer310.

Flexible portion 313 may be between two adjacent piezoelectric portionsof the plurality of piezoelectric portions 311, may improve an impactresistance of the piezoelectric portions 311, and may provideflexibility to flexible vibration module 300. Flexible portion 313 andthe plurality of piezoelectric portions 311 may be alternately disposed(or arranged) on the same plane (or the same layer). Flexible portion313 may be configured to fill a gap between two adjacent piezoelectricportions of the plurality of piezoelectric portions 311 and may beconnected to or attached on a piezoelectric portion 311 adjacentthereto. For example, flexible portion 313 may have a line patternhaving a width W6 corresponding to a gap between two adjacentpiezoelectric portions 311.

For example, a plurality of flexible portions each between two adjacentpiezoelectric portions of the plurality of piezoelectric portions 311may each have the same size within a process error range (or anallowable error range or a tolerance) occurring in a manufacturingprocess, and for example, may have a width, an area, or a volume.However, the present example embodiment is not limited thereto, and theplurality of flexible portions 313 may have different sizes or may havea size corresponding to a size of two adjacent piezoelectric portions311. Therefore, a size of each of the plurality of flexible portions 313may be adjusted based on a needed condition of at least one of avibration characteristic, flexibility, and a size of flexible vibrationmodule 300. For example, in the display apparatus or flexible vibrationmodule 300 needing a piezoelectric characteristic rather thanflexibility, the width W6 of each piezoelectric portion 311 may beadjusted to be greater than a width W7 of the flexible portion 313. Inanother example embodiment, in the display apparatus or flexiblevibration module 300 needing flexibility rather than a piezoelectriccharacteristic, the width W6 of each piezoelectric portion 311 may beadjusted to be less than the width W7 of the flexible portion 313.Accordingly, a size of piezoelectric composite layer 310 may be adjustedbased on a characteristic needed for the display apparatus, and thus, itmay be easy to design piezoelectric composite layer 310.

The flexible portion 313 according to the present example embodiment mayinclude a lower flexible portion 313 a and an upper flexible portion 313b. A plurality of lower flexible portions 313 a may each be disposedbetween the plurality of lower piezoelectric portions 311 a of theplurality of piezoelectric portions 311. The plurality of lower flexibleportions 313 a and the plurality of lower piezoelectric portions 311 amay be alternately disposed (or arranged) on the same plane (or the samelayer). Each of the plurality of lower flexible portions 313 a may beconfigured to fill a gap between two adjacent lower piezoelectricportions of the plurality of lower piezoelectric portions 311 a and maybe connected to or attached on a lower piezoelectric portion 311 aadjacent thereto. Therefore, each of the lower flexible portions 313 amay have the same thickness as that of a lower piezoelectric portion 311a adjacent thereto. Each lower flexible portion 313 a and acorresponding lower piezoelectric portion 311 a of each of the pluralityof piezoelectric portions 311 may configure a lower piezoelectriccomposite layer 310 a of piezoelectric composite layer 310.

A plurality of upper flexible portions 313 b may each be disposedbetween the plurality of upper piezoelectric portions 311 b of theplurality of piezoelectric portions 311. The plurality of upper flexibleportions 313 b and the plurality of upper piezoelectric portions 311 bmay be alternately disposed (or arranged) on the same plane (or the samelayer). Each of the plurality of upper flexible portions 313 b may beconfigured to fill a gap between two adjacent upper piezoelectricportions of the plurality of upper piezoelectric portions 311 b and maybe connected to or attached on an upper piezoelectric portion 311 badjacent thereto. Therefore, each of the upper flexible portions 313 bmay have the same thickness as that of an upper piezoelectric portion311 b adjacent thereto. Each upper flexible portion 313 b and acorresponding upper piezoelectric portion 311 b of each of the pluralityof piezoelectric portions 311 may configure an upper piezoelectriccomposite layer 310 b of piezoelectric composite layer 310.

In piezoelectric composite layer 310 according to the present exampleembodiment, the lower piezoelectric portion 311 a and the upperpiezoelectric portion 311 b of each of the plurality of piezoelectricportions 311 may have a vertical stacked structure. As a result, anexpansive force (or a tension) and a contractile force (or a compressiveforce) each based on a bimorph structure may increase more, therebyenhancing a sound pressure characteristic.

Piezoelectric composite layer 310 according to the present exampleembodiment may further include a first counter electrode layer 360, asecond counter electrode layer 370, and an insulation layer 380. Thefirst counter electrode layer 360 may be electrically connected to thelower piezoelectric portion 311 a of each of the plurality ofpiezoelectric portions 311. For example, the first counter electrodelayer 360 may be on the lower piezoelectric composite layer 310 a ofpiezoelectric composite layer 310 and may be electrically connected tothe lower piezoelectric portion 311 a of each of the plurality ofpiezoelectric portions 311. The first counter electrode layer 360 may beformed of the same material as that of the first electrode layer 320.The lower piezoelectric portion 311 a of each of the plurality ofpiezoelectric portions 311 may vibrate according to an electrical signalapplied to the first electrode layer 320 and the first counter electrodelayer 360.

The second counter electrode layer 370 may be electrically connected tothe upper piezoelectric portion 311 b of each of the plurality ofpiezoelectric portions 311. For example, the second counter electrodelayer 370 may be on the upper piezoelectric composite layer 310 b ofpiezoelectric composite layer 310 and may be electrically connected tothe upper piezoelectric portion 311 b of each of the plurality ofpiezoelectric portions 311. The second counter electrode layer 370 maybe formed of the same material as that of the second electrode layer330. The upper piezoelectric portion 311 b of each of the plurality ofpiezoelectric portions 311 may vibrate according to an electrical signalapplied to the second electrode layer 330 and the second counterelectrode layer 370.

The insulation layer 380 may be between the first counter electrodelayer 360 and the second counter electrode layer 370 and mayelectrically insulate the first counter electrode layer 360 from thesecond counter electrode layer 370. The insulation layer 380 may includean electrical insulating material that has adhesiveness and iscompressible and restorable. For example, the insulation layer 380 mayinclude at least one of an epoxy-based polymer, an acryl-based polymer,and a silicon-based polymer.

In another example embodiment, in flexible vibration module 300, theinsulation layer 380 and the second counter electrode layer 370 may beomitted. For example, as illustrated in FIG. 11, the first counterelectrode layer 360 may be electrically connected to a second surface(or a front surface) of each of the lower piezoelectric portions 311 ain the lower piezoelectric composite layer 310 a and may be electricallyconnected to a first surface (or a rear surface) of each of the upperpiezoelectric portions 311 b in the upper piezoelectric composite layer310 b. Therefore, the first opposite electrode layer 360 may be used asa common electrode (or a shared electrode) of the lower piezoelectriccomposite layer 310 a and the upper piezoelectric composite layer 310 b,and in each of the plurality of piezoelectric portions 311, apolarization direction of each of the lower piezoelectric portions 311 amay be a direction opposite to a polarization direction of each of theupper piezoelectric portions 311 b.

In flexible vibration module 300 according to the fifth exampleembodiment, an arrangement structure of the piezoelectric portions 311is not limited to the arrangement structure illustrated in FIG. 9 andmay be changed to various structures, based on a needed condition of atleast one of a vibration characteristic, flexibility, and a size offlexible vibration module 300. For example, a thickness gradient or avibration frequency of each of the lower piezoelectric portion 311 a ineach of the piezoelectric portions 311 may not be adjusted toprogressively decrease in a direction from ends EP1 and EP2 to the firstcenter portion CP1 of piezoelectric composite layer 310 and may beadjusted to be randomly changed, or may be adjusted to progressivelydecrease in a direction from the one end EP1 to the other end EP2 ofpiezoelectric composite layer 310 or to be randomly changed.

In flexible vibration module 300 according to the fifth exampleembodiment of the present disclosure, the plurality of piezoelectricportions 311 may have various vibration frequencies, based on athickness gradient of each of the lower piezoelectric portion 311 a andthe upper piezoelectric portion 311 b each having a vertical stackedstructure. As a result, the plurality of piezoelectric portions 311 mayvibrate display panel 100 by using a vibration having various vibrationfrequencies with an electric field based on a signal applied to each ofthe plurality of piezoelectric portions 311. Accordingly, a soundpressure planarization (or flatness) characteristic and a sound pressurecharacteristic of a sound generated based on a vibration of displaypanel 100 may increase and a sound reproduction band may expand.Piezoelectric composite layer 310 may have the bimorph structure, andthus, flexible vibration module 300 according to the fifth exampleembodiment of the present disclosure may more increase an expansiveforce (or a tension) and a contractile force (or a compressive force) tosufficiently vibrate display panel 100 in a vertical direction (or aforward-backward direction). Accordingly, a sound pressure planarization(or flatness) characteristic and a sound pressure characteristic of asound generated based on a vibration of display panel 100 may increaseand a sound reproduction band may expand.

Flexible vibration module 300 according to the first to fifth exampleembodiments of the present disclosure may have a thin film type havingrelatively high flexibility, and thus, may be applied to a displayapparatus that uses a display panel as a vibration plate. For example,flexible vibration module 300 according to example embodiments of thepresent disclosure may be applied to a flexible display, and forexample, may be applied to a curved display bent at a certain curvatureradius. However, flexible vibration module 300 is not limited theretoand may be applied to a rollable display wound in a spiral form, abendable display, a wearable display wound around a wrist, or acommercial display having a plurality of curved portions. For example,the flexile vibration module 300 may be bent based on a certaincurvature radius or to be bent based on winding in a spiral shape orunwinding and may be in a display panel to correspond to or overlap awhole display area of the display panel or may be in the display panelto maintain a predetermined distance to the display panel.

FIG. 12 is another cross-sectional view taken along line I-I′ in FIG. 1,and FIG. 13 illustrates a flexible vibration module and a partition eachillustrated in FIG. 12. FIGS. 12 and 13 illustrate an example embodimentimplemented by modifying flexible vibration module in the displayapparatus illustrated in FIGS. 1 and 2. As illustrated in FIGS. 12 and13, in a display apparatus according to another example embodiment ofthe present disclosure, a flexible vibration module 300 may include afirst flexible vibration module 300-1 and a second flexible vibrationmodule 300-1 each on a rear surface of a display panel 100.

The rear surface (or a back surface) of display panel 100 may includefirst and second regions A1 and A2. For example, the rear surface (orthe back surface) of display panel 100 may be divided into the first andsecond regions A1 and A2. For example, in the rear surface of displaypanel 100, the first region A1 may be a left region, and the secondregion A2 may be a right region. The first and second regions A1 and A2may be symmetrical laterally with respect to a center line CL of displaypanel 100 in a first direction X.

The first flexible vibration module 300-1 may be in the first region A1of display panel 100. The first flexible vibration module 300-1 mayvibrate the first region A1 of display panel 100 to generate a firstpanel vibration sound PVS1 or a first haptic feedback in the firstregion A1 of display panel 100. For example, the first panel vibrationsound PVS1 may be a left sound. The first flexible vibration module300-1 may be configured as one of flexible vibration modules 300according to the first to fifth example embodiments of the presentdisclosure illustrated in FIGS. 3 to 11.

The first flexible vibration module 300-1 may be close to a centerportion or an edge or a periphery of display panel 100 in the firstregion A1 of display panel 100 with respect to the first direction X. Asize of the first flexible vibration module 300-1 may have a size equalto or greater than half of the first region A1, but is not limitedthereto, and may be adjusted based on a sound characteristic needed forthe display apparatus. For example, in the first region A1 of displaypanel 100, as a size of the first flexible vibration module 300-1increases, a vibration region (or a vibration area) of the first regionA1 may increase, thereby enhancing a low-pitched sound bandcharacteristic of a left sound. On the other hand, in the first regionA1 of display panel 100, as a size of the first flexible vibrationmodule 300-1 decreases, a vibration region (or a vibration area) of thefirst region A1 may decrease, thereby enhancing a high-pitched soundband characteristic of the left sound. Accordingly, a size of the firstflexible vibration module 300-1 may be adjusted based on a desiredcharacteristic of a sound band according to a vibration of display panel100.

The second flexible vibration module 300-2 may be in the second regionA2 of display panel 100. The second flexible vibration module 300-2 mayvibrate the second region A2 of display panel 100 to generate a secondpanel vibration sound or a second haptic feedback in the second regionA2 of display panel 100. For example, the second panel vibration soundmay be a right sound. The second flexible vibration module 300-2 may bethe same as the first flexible vibration module 300-1 and may besymmetrical with the first flexible vibration module 300-1 with respectto the center line CL of display panel 100. The second flexiblevibration module 300-2 according to an example embodiment may be closeto a center portion or an edge or a periphery of display panel 100 inthe second region A2 of display panel 100 with respect to the firstdirection X and may be symmetrical with the first flexible vibrationmodule 300-1 with respect to the center line CL of display panel 100.

The display apparatus according to another example embodiment of thepresent disclosure may output, through the first and second flexiblevibration modules 300-1 and 300-2, a left sound and a right sound to aforward region FD in front of display panel 100 to provide a stereosound to a user. The display apparatus according to another exampleembodiment of the present disclosure may further include a partition 700for separating a vibration region based on the first flexible vibrationmodule 300-1 from a vibration region based on the second flexiblevibration module 300-2. The partition 700 according to an exampleembodiment may include a first partition member 710 between the firstflexible vibration module 300-1 and the second flexible vibration module300-2.

The first partition member 710 may be on a rear center line CL ofdisplay panel 100 and may separate a first panel vibration (or a panelvibration sound) generated by the first flexible vibration module 300-1from a second panel vibration (or a panel vibration sound) generated bythe second flexible vibration module 300-2. The first partition member710 according to an example embodiment may be between a rear center ofdisplay panel 100 and a rear structure 500 and may spatially separate agap space GS between display panel 100 and the rear structure 500. Forexample, the first partition member 710 may prevent a vibrationgenerated in the first region A1 of display panel 100 by the firstflexible vibration module 300-1 from being transferred to the secondregion A2 of display panel 100, or may prevent a vibration generated inthe second region A2 of display panel 100 by the second flexiblevibration module 300-2 from being transferred to the first region A1 ofdisplay panel 100. Therefore, the first partition member 710 mayattenuate or absorb a vibration of display panel 100 at a center ofdisplay panel 100, and thus, may block or prevent the transfer of asound of the first region A1 to the second region A2 or may block orprevent the transfer of a sound of the second region A2 to the firstregion A1. The first partition member 710 may be referred to as a centerpartition, a sound separation member, a center enclosure, a centerbaffle, or a partition.

For example, the first partition member 710 may be formed of one ofpolyurethane, and/or polyolefin. In another example embodiment, thefirst partition member 710 may be formed of a double-sided adhesive tapeor a single-sided adhesive tape, and for example, may be formed of amaterial having an elastic force that enables compression to be made toa certain degree. Therefore, the first partition member 710 may separatea left sound and a right sound to more enhance a sound outputcharacteristic of the display apparatus, and a display apparatusincluding the first partition member 710 may separate the left and rightsounds by using the first partition member 710 to output a two-channelstereo sound to the forward region in front of display panel 100.

The partition 700 according to an example embodiment may further includea second partition member 720 surrounding a region between display panel100 and the rear structure 500. The second partition member 720 may bedisposed along a space between a rear edge or a rear periphery ofdisplay panel 100 and a front edge or a front periphery of the rearstructure 500 to surround all of the first and second flexible vibrationmodules 300-1 and 300-2. The second partition member 720 may be referredto as an edge partition, a sound blocking member, an edge enclosure, ora baffle.

The second partition member 720 may provide first and second air gapsAG1 and AG2 between display panel 100 and the rear structure 500 alongwith the first partition member 710. For example, each of the first andsecond air gaps AG1 and AG2 may be referred to as a vibration space, asound pressure space, a sound box, a sound part, a resonance box, or aresonance part. The first air gap AG1 may be in the first region A1 ofdisplay panel 100 surrounded by the first partition member 710 and thesecond partition member 720 in the first region A1 of display panel 100.The second air gap AG2 may be in the second region A2 of display panel100 surrounded by the first partition member 710 and the secondpartition member 720 in the second region A2 of display panel 100.

The first flexible vibration module 300-1 may be surrounded by the firstpartition member 710 and a portion, providing the first air gap AG1, ofthe second partition member 720, and the second flexible vibrationmodule 300-2 may be surrounded by the first partition member 710 and theother portion, providing the second air gap AG2, of the second partitionmember 720. In another example embodiment, the second partition member720 may be omitted.

The second partition member 720 may be between display panel 100 and therear structure 500 and may individually (or independently) surround eachof the first and second flexible vibration modules 300-1 and 300-2 alongwith the first partition member 710 to secure a vibration space of eachof the first and second flexible vibration modules 300-1 and 300-2. Thismay enhance a sound pressure characteristic of left and right sounds andmay prevent a sound or a sound pressure from being leaked to the outsidethrough the side surface between display panel 100 and the rearstructure 500, thereby enhancing a sound output characteristic of thedisplay apparatus.

The partition 700 according to an example embodiment may further includea third partition member 730 surrounding the first flexible vibrationmodule 300-1 and a fourth partition member 740 surrounding the secondflexible vibration module 300-2. The third partition member 730 may bebetween display panel 100 and the rear structure 500 to overlap thefirst air gap AG1 or correspond to the first air gap AG1 and mayindividually (or independently) surround the first flexible vibrationmodule 300-1. The third partition member 730 according to an exampleembodiment may have a circular shape surrounding the first flexiblevibration module 300-1, but is not limited thereto, and may have a shapethat is the same as or different from a whole shape of the firstflexible vibration module 300-1. For example, when the first flexiblevibration module 300-1 has a rectangular shape, the third partitionmember 730 may have a rectangular shape having a size that is relativelygreater than that of the first flexible vibration module 300-1.

The third partition member 730 may limit (or define) a vibration region(or a vibration area) of display panel 100 based on the first flexiblevibration module 300-1. For example, in the first region A1 of displaypanel 100, as a size of the third partition member 730 increases, avibration region of the first region A1 may increase, and thus, alow-pitched sound band characteristic of a left sound may be enhanced.On the other hand, in the first region A1 of display panel 100, as asize of the third partition member 730 decreases, the vibration regionof the first region A1 may decrease, and thus, a high-pitched sound bandcharacteristic of the left sound may be enhanced. Accordingly, a size ofthe third partition member 730 may be adjusted based on a desiredcharacteristic of a sound band, based on a vibration of display panel100.

The fourth partition member 740 may be between display panel 100 and therear structure 500 to overlap the second air gap AG2 or correspond tothe second air gap AG2 and may individually (or independently) surroundthe second flexible vibration module 300-2. In order for a left sound tobe symmetrical with a right sound, the fourth partition member 740 mayhave the same shape as that of the third partition member 730 and asymmetrical structure with the third partition member 730 with respectto the rear center line CL of display panel 100.

The fourth partition member 740 may limit (or define) a vibration region(or a vibration area) of display panel 100 based on the second flexiblevibration module 300-2. For example, in the second region A2 of displaypanel 100, as a size of the fourth partition member 740 increases, avibration region of the second region A2 may increase, and thus, thelow-pitched sound band characteristic of the right sound may beenhanced. On the other hand, in the second region A2 of display panel100, as a size of the fourth partition member 740 decreases, thevibration region of the second region A2 may decrease, and thus, thehigh-pitched sound band characteristic of the right sound may beenhanced. Accordingly, a size of the fourth partition member 740 may beadjusted based on a desired characteristic of a sound band, based on avibration of display panel 100.

The third and fourth partition members 730 and 740 may limit a vibrationregion (or a vibration area) of each of the first and second flexiblevibration modules 300-1 and 300-2. This may enhance lateral symmetricityof a left sound and a right sound each generated based on a vibration ofdisplay panel 100 and may optimize a sound pressure characteristic and asound reproduction band of each of the left and right sounds.

In some example embodiments, one or more of partition members 710, 720,730, and 740 may be formed of a double-sided adhesive tape or asingle-sided adhesive tape, and for example, may be formed of a materialhaving an elastic force that enables compression to be made to a certaindegree.

FIG. 14 illustrates a flexible vibration module and a partition eachillustrated in FIG. 12 and illustrates an example embodiment implementedby modifying the first partition member illustrated in FIG. 13. Asillustrated in FIG. 14, in a display apparatus according to anotherexample embodiment of the present disclosure, a first partition member710 may include first and second sub-partition members 711 and 713spaced apart from each other on a rear center line CL of a display panel100. The first partition member 710 including the first and secondsub-partition members 711 and 713 may be referred to as at least onefirst partition member.

The first and second sub-partition members 711 and 713 may be between arear center of display panel 100 and the rear structure 500. Forexample, the first and second sub-partition members 711 and 713 may bein parallel between the rear center of display panel 100 and the rearstructure 500. The first and second sub-partition members 711 and 713may provide or form first to third air gaps AG1 to AG3 between displaypanel 100 and the rear structure 500 along with the second partitionmember 720.

The first air gap AG1 may be in a first region A1 of display panel 100surrounded by the first sub-partition member 711 and the secondpartition member 720 in the first region A1 of display panel 100. Thesecond air gap AG2 may be in a second region A2 of display panel 100surrounded by the second sub-partition member 713 and the secondpartition member 720 in the second region A2 of display panel 100.

The third air gap AG3 may be in a center region of display panel 100surrounded by the first and second sub-partition members 711 and 713 andthe second partition member 720. For example, the third air gap AG3 maybe provided between the second air gap AG2 and the first air gap AG1including a rear center line CL of display panel 100. The third air gapAG3 may be referred to as a sound separation space, a sound blockingspace, or a sound interference prevention space. The third air gap AG3may spatially separate the first air gap AG1 from the second air gapAG2, and thus, may prevent a resonance phenomenon or an interferencephenomenon in a certain frequency band, which occurs in each of thefirst air gap AG1 and the second air gap AG2. In another exampleembodiment, the second partition member 720 may be omitted.

The first flexible vibration module 300-1 may be surrounded by the firstsub-partition member 711 and a portion, providing the first air gap AG1,of the second partition member 720. The second flexible vibration module300-2 may be surrounded by the second sub-partition member 713 and theother portion, providing the second air gap AG2, of the second partitionmember 720. The first partition member 710 including the first andsecond sub-partition members 711 and 713 together with the secondpartition member 720 may provide the first air gaps AG1, the second airgaps AG2, and the third air gap AG3 between the first and second airgaps AG1 and AG2 that individually surround each of the first and secondflexible vibration modules 300-1 and 300-2. This may secure a vibrationspace of each of the first and second flexible vibration modules 300-1and 300-2 to increase a sound pressure characteristic of left and rightsounds and to prevent a resonance phenomenon or an interferencephenomenon of the left and right sounds, thereby enhancing a soundpressure characteristic of the left and right sounds. Accordingly, asound output characteristic of the display apparatus may be moreenhanced.

FIGS. 15A to 15C illustrate modified example embodiments of first andsecond flexible vibration modules in FIG. 14 and illustrate an exampleembodiment implemented by modifying an arrangement structure of apiezoelectric portion in the piezoelectric composite layer in FIG. 14.As illustrated in FIG. 15A, in each of first and second flexiblevibration modules 300-1 and 300-2 according to a first modified exampleembodiment, except for that a length of each of a plurality ofpiezoelectric portions 311 increases progressively in a direction froman edge or a periphery to a center line CL of a display panel 100 on thebasis of a length gradient, each of the first and second flexiblevibration modules 300-1 and 300-2 is the same as the flexible vibrationmodule illustrated in FIG. 3 or 13. Therefore, the plurality ofpiezoelectric portions 311 according to the first modification exampleembodiment may each have different vibration frequencies on the basis ofdifferent lengths. As a result, a sound pressure characteristic of eachof a left sound and a right sound each generated based on a vibration ofdisplay panel 100 may increase and a sound reproduction band may expand.In FIG. 15A, the second partition member 720 may be omitted.

As illustrated in FIG. 15B, in each of first and second flexiblevibration modules 300-1 and 300-2 according to a second modificationexample embodiment, except that a length of each of a plurality ofpiezoelectric portions 311 increases progressively in a direction froman edge or a periphery to a center line CL of a display panel 100 on thebasis of a length gradient, each of the first and second flexiblevibration modules 300-1 and 300-2 is the same as the flexible vibrationmodule illustrated in FIG. 6. Therefore, the plurality of piezoelectricportions 311 according to the second modification example embodiment mayeach have different vibration frequencies on the basis of differentlengths. As a result, a sound pressure characteristic of each of a leftsound and a right sound each generated based on a vibration of displaypanel 100 may increase and a sound reproduction band may expand. In FIG.15B, the second partition member 720 may be omitted.

As illustrated in FIG. 15C, in each of first and second flexiblevibration modules 300-1 and 300-2 according to a third modificationexample embodiment, except for that a width of each of a plurality ofpiezoelectric portions 311 increases progressively in a direction froman edge or a periphery to a center line CL of a display panel 100 on thebasis of a width gradient, each of the first and second flexiblevibration modules 300-1 and 300-2 is the same as the flexible vibrationmodule illustrated in FIG. 7. Therefore, the plurality of piezoelectricportions 311 according to the third modification example embodiment mayeach have different vibration frequencies on the basis of differentwidths. As a result, a sound pressure characteristic of each of a leftsound and a right sound each generated based on a vibration of displaypanel 100 may increase and a sound reproduction band may expand. In FIG.15C, the second partition member 720 may be omitted.

FIGS. 16A to 16C illustrate various display apparatuses to which aflexible vibration module according to example embodiments of thepresent disclosure may be applied and illustrate a display apparatus towhich the flexible vibration module illustrated in each of FIGS. 3 to 11is applied. A flexible vibration module according to example embodimentsof the present disclosure may be a film type having flexibility, and maybe applied to various application apparatuses.

As illustrated in FIG. 16A, a flexible vibration module 300 according toexample embodiments of the present disclosure may be applied to acommercial display or a flexible display including a display panel 100including a plurality of curved surface portions CSP that are concave orconvex. For example, flexible vibration module 300 may be bent in ashape having a curvature value (or a curvature radius) matching orcorresponding to a convex portion or a concave portion of each of thecurved surface portions CSP of display panel 100 and may be in theconvex portion or the concave portion of each of the curved surfaceportions CSP of display panel 100. In another example embodiment,flexible vibration module 300 may have a shape matching the curvaturevalue (or the curvature radius) of each of the curved surface portionsCSP of display panel 100 and may be on a whole rear surface of displaypanel 100.

As illustrated in FIG. 16B, flexible vibration module 300 according toexample embodiments of the present disclosure may be applied to arollable display including a display panel 100 that is wound in a spiralshape or unwound. For example, flexible vibration module 300 accordingto example embodiments of the present disclosure may have a shape havinga curvature value (or a curvature radius) of display panel 100 that iswound in a spiral shape or unwound. A plurality of flexible vibrationmodules 300 may be arranged at certain intervals or distances on a rearsurface of display panel 100. In another example embodiment, flexiblevibration module 300 may have a shape matching or corresponding to thecurvature value (or the curvature radius) of display panel 100 and maybe on the whole rear surface of display panel 100.

As illustrated in FIG. 16C, flexible vibration module 300 according toexample embodiments of the present disclosure may be applied to awearable display including a display panel 100 that is wound around awrist of a user and is bent in a “C”-shape. For example, flexiblevibration module 300 according to example embodiments of the presentdisclosure may have a shape having a curvature value (or a curvatureradius) of display panel 100 that is bent in the “C”-shape. A pluralityof flexible vibration modules 300 may be arranged at certain intervalsor distances on a rear surface of display panel 100. In another exampleembodiment, flexible vibration module 300 may have a shape matching thecurvature value (or the curvature radius) of display panel 100 that isbent in the “C”-shape and may be disposed on the whole rear surface ofdisplay panel 100.

FIG. 17 is a graph showing a sound pressure characteristic of a displaypanel according to an example embodiment of the present disclosure and asound pressure characteristic of a display panel according to acomparative example. In the sound pressure measurement of FIG. 17, AudioPrecision Company's APx525 was used, a sine sweep was applied at 20 Hzto 20 kHz, and a sound pressure was measured at a position space apartfrom a display panel, a flexible vibration module, and a film speaker by50 cm. The sine sweep may be a process of performing a sweep for a shorttime. In FIG. 17, the abscissa axis (x-axis) represents a frequency inhertz (Hz), and the ordinate axis (y-axis) represents a sound pressurelevel in decibels (dB).

In an example embodiment (a thick solid line) of the present disclosure,a display panel where a partition is not in the display apparatusillustrated in FIG. 15A has been prepared. In the comparative example (adotted line), a display panel where a flexible vibration moduleincluding a plurality of piezoelectric portions having the same lengthand having no length gradient is attached on each of a left region and aright region has been prepared.

As illustrated in FIG. 17, comparing a display panel (a dotted line)according to the comparative example, a display panel (a thick solidline) according to an example embodiment of the present disclosure has asound pressure level of 50 dB or more in a full audible frequency andhas a sound pressure level of about 10 dB higher in a high-pitched soundband as well as a low-pitched sound band, and dipping of a soundpressure level is reduced in the full audible frequency to improveflatness of a sound pressure level. Here, flatness of a soundcharacteristic may be a level of a deviation between a highest soundpressure level and a lowest sound pressure level.

Therefore, in the flexible vibration module and the display apparatusincluding the same according to the present disclosure, a plurality ofpiezoelectric portions configuring a piezoelectric composite layer hasvarious vibration frequencies on the basis of a size gradient. As aresult, a sound pressure characteristic increases in a full audiblefrequency and a sound reproduction band expands. The flexible vibrationmodule and the display apparatus including the same according to thepresent disclosure may be applied to various applications. For example,a display panel where the flexible vibration module according to thepresent disclosure is disposed and a display apparatus including thesame may be applied to mobile apparatuses, video phones, smart watches,watch phones, wearable devices, foldable apparatuses, rollableapparatuses, bendable apparatuses, flexible apparatuses, curvedapparatuses, electronic notebooks, electronic books, portable multimediaplayers (PMPs), personal digital assistants (PDAs), MP3 player, mobilemedical apparatuses, electronic organizers, desktop personal computers(PCs), laptop PCs, netbook computers, workstations, navigationapparatuses, automotive navigation apparatuses, automotive displays,televisions (TVs), wall paper displays, signage apparatuses, gamemachines, notebook computers, monitors, cameras, camcorders, homeappliances, etc.

The flexible vibration module according to an example embodiment of thepresent disclosure may be applied to organic light emitting lightingapparatuses or inorganic light emitting lighting apparatuses. Where theflexible vibration module according to the present disclosure is appliedto a lighting apparatus, the flexible vibration module may act aslighting and a speaker. In some example embodiments, the flexiblevibration module according to the present disclosure may be applied to amobile apparatus, and the flexible vibration module may act as a speakeror a receiver.

A flexible vibration module and a display apparatus including the sameaccording to the present disclosure will be described below. Accordingto some example embodiments of the present disclosure, a flexiblevibration module may include: a piezoelectric composite layer,including: a plurality of piezoelectric portions each having apiezoelectric characteristic, wherein at least two of the plurality ofpiezoelectric portions have different sizes; and a flexible portionbetween the plurality of piezoelectric portions. Each of the pluralityof piezoelectric portions may have a different size and a differentvibration frequency. At least two of the plurality of piezoelectricportions may have different lengths, different widths, and differentthicknesses.

According to some example embodiments of the present disclosure, one ofa length, a width, and a thickness of each of the plurality ofpiezoelectric portions may increase or decrease progressively in adirection from at least one end of the piezoelectric composite layer toa center portion of the piezoelectric composite layer. One of a length,a width, and a thickness of each of the plurality of piezoelectricportions may randomly vary between one end and another end of thepiezoelectric composite layer. One of a length, a width, and a thicknessof each of the plurality of piezoelectric portions may increase ordecrease progressively in a direction from one end of the piezoelectriccomposite layer to another end opposite to the one end.

According to some example embodiments of the present disclosure, each ofthe plurality of piezoelectric portions may include: a lowerpiezoelectric portion; and an upper piezoelectric portion on the lowerpiezoelectric portion. Each of the plurality of piezoelectric portionsmay have a same thickness. At least two of the lower piezoelectricportions may have different thicknesses. The plurality of piezoelectricportions may have a same thickness; and a thickness of each of the lowerpiezoelectric portions may progressively or randomly change in adirection from one end of the piezoelectric composite layer to anotherend opposite to the one end. The flexible vibration module may furtherinclude an electrode between the lower piezoelectric portion and theupper piezoelectric portion. The flexible vibration module may furtherinclude: a first electrode between the lower piezoelectric portion andthe upper piezoelectric portion; a second electrode between the lowerpiezoelectric portion and the upper piezoelectric portion; and aninsulating layer between the first electrode and the second electrode.

According to some example embodiments of the present disclosure, aflexible vibration module, may include: a piezoelectric composite layer,including: a plurality of piezoelectric portions each having apiezoelectric characteristic; and a flexible portion between theplurality of piezoelectric portions, wherein the piezoelectric compositelayer has a plurality of vibration frequencies. At least two of theplurality of piezoelectric portions may have different vibrationfrequencies. A vibration frequency of each of the plurality ofpiezoelectric portions may progressively or randomly change in adirection from one end of the piezoelectric composite layer to the otherend opposite to the one end. Each of the plurality of piezoelectricportions may include: a lower piezoelectric portion; and an upperpiezoelectric portion on the lower piezoelectric portion. The pluralityof piezoelectric portions may have a same thickness; and a thickness ofeach of the lower piezoelectric portions progressively thickens or thinsin a direction from at least one end of the piezoelectric compositelayer to a center portion of the piezoelectric composite layer. Each ofthe plurality of piezoelectric portions may include an inorganicmaterial; and the flexible portion may include at least one of anorganic piezoelectric material and an organic non-piezoelectricmaterial.

According to some example embodiments of the present disclosure, adisplay apparatus may include: a flexible vibration module, including: apiezoelectric composite layer, including: a plurality of piezoelectricportions each having a piezoelectric characteristic, wherein at leasttwo of the plurality of piezoelectric portions have different sizes; anda flexible portion between the plurality of piezoelectric portions; anda display panel, wherein the display panel may include a display areaconfigured to display an image and vibrate according to a vibration ofthe flexible vibration module. The display apparatus may further includea touch electrode configured to sense a touch, wherein the flexiblevibration module may be configured to vibrate according to the touch.Each of the plurality of piezoelectric portions may include an inorganicmaterial; and the flexible portion may include at least one of anorganic piezoelectric material and an organic non-piezoelectricmaterial.

According to some example embodiments of the present disclosure, thedisplay panel may include a first region and a second region; theflexible vibration module may be a first flexible vibration module inthe first region of the display panel; and a second flexible vibrationmodule may be in the second region of the display panel. The displayapparatus may further include: a rear structure on a rear surface of thedisplay panel; and at least one partition member between the displaypanel and the rear structure and between the first flexible vibrationmodule and the second flexible vibration module. The display apparatusmay further include: a rear structure on a rear surface of the displaypanel; and a partition between the display panel and the rear structure,wherein the partition surrounds at least one of the first flexiblevibration module and the second flexible vibration module. The displayapparatus may further include another partition between the displaypanel and the rear structure, the another partition surrounding both thefirst and second flexible vibration modules, and the partition.

The above-described features, structure, and effect of the presentdisclosure are included in at least one example embodiment of thepresent disclosure, but are not limited to only one example embodiment.Furthermore, the features, structure, and effect described in at leastone example embodiment of the present disclosure may be implementedthrough combination or modification of other example embodiments bythose skilled in the art. Therefore, content associated with thecombination and modification should be construed as being within thescope of the present disclosure. It will be apparent to those skilled inthe art that various modifications and variations can be made in thepresent disclosure without departing from the spirit or scope of thedisclosures. Thus, it is intended that the present disclosure covers themodifications and variations of this disclosure provided they comewithin the scope of the appended claims and their equivalents.

1. A flexible vibration module, comprising: a piezoelectric compositelayer, including: a plurality of piezoelectric portions each having apiezoelectric characteristic, wherein at least two of the plurality ofpiezoelectric portions have different sizes; and a flexible portionbetween the plurality of piezoelectric portions, a first electrode on afirst surface of the plurality of piezoelectric portions and a firstsurface of the flexible portion; and a second electrode on a secondsurface of the plurality of piezoelectric portions and a second surfaceof the flexible portion, wherein each of the first surface and thesecond surface is configured to have a plane surface structure.
 2. Theflexible vibration module of claim 1, wherein each of the plurality ofpiezoelectric portions has a different size and a different vibrationfrequency.
 3. The flexible vibration module of claim 1, wherein at leasttwo of the plurality of piezoelectric portions have different lengths,different widths, and different thicknesses.
 4. The flexible vibrationmodule of claim 1, wherein one of a length, a width, and a thickness ofeach of the plurality of piezoelectric portions increases or decreasesprogressively in a direction from at least one end of the piezoelectriccomposite layer to a center portion of the piezoelectric compositelayer.
 5. The flexible vibration module of claim 1, wherein one of alength, a width, and a thickness of each of the plurality ofpiezoelectric portions randomly varies between one end and another endof the piezoelectric composite layer.
 6. The flexible vibration moduleof claim 1, wherein one of a length, a width, and a thickness of each ofthe plurality of piezoelectric portions increases or decreasesprogressively in a direction from one end of the piezoelectric compositelayer to another end opposite to the one end.
 7. The flexible vibrationmodule of claim 1, wherein each of the plurality of piezoelectricportions comprises: a lower piezoelectric portion; and an upperpiezoelectric portion on the lower piezoelectric portion.
 8. Theflexible vibration module of claim 7, wherein each of the plurality ofpiezoelectric portions has a same thickness.
 9. The flexible vibrationmodule of claim 7, wherein at least two of the lower piezoelectricportions have different thicknesses.
 10. The flexible vibration moduleof claim 7, wherein: the plurality of piezoelectric portions have a samethickness; and a thickness of each of the lower piezoelectric portionsprogressively or randomly changes in a direction from one end of thepiezoelectric composite layer to another end opposite to the one end.11. The flexible vibration module of claim 7, further comprising anelectrode between the lower piezoelectric portion and the upperpiezoelectric portion.
 12. The flexible vibration module of claim 7,further comprising: a first counter electrode between the lowerpiezoelectric portion and the upper piezoelectric portion; a secondcounter electrode between the lower piezoelectric portion and the upperpiezoelectric portion; and an insulating layer between the first counterelectrode and the second counter electrode.
 13. A flexible vibrationmodule, comprising: a piezoelectric composite layer, including: aplurality of piezoelectric portions each having a piezoelectriccharacteristic; and a flexible portion between the plurality ofpiezoelectric portions, a first electrode on a first surface theplurality of piezoelectric portions and a first surface of the flexibleportion; and a second electrode on a second surface of the plurality ofpiezoelectric portions and a second surface of the flexible portion,wherein each of the first surface and the second surface is configuredto have a plane surface structure, and wherein the piezoelectriccomposite layer has a plurality of vibration frequencies.
 14. Theflexible vibration module of claim 13, wherein at least two of theplurality of piezoelectric portions have different vibrationfrequencies.
 15. The flexible vibration module of claim 13, wherein avibration frequency of each of the plurality of piezoelectric portionsprogressively or randomly changes in a direction from one end of thepiezoelectric composite layer to the other end opposite to the one end.16. The flexible vibration module of claim 13, wherein each of theplurality of piezoelectric portions comprises: a lower piezoelectricportion; and an upper piezoelectric portion on the lower piezoelectricportion.
 17. The flexible vibration module of claim 16, wherein: theplurality of piezoelectric portions have a same thickness; and athickness of each of the lower piezoelectric portions progressivelythickens or thins in a direction from at least one end of thepiezoelectric composite layer to a center portion of the piezoelectriccomposite layer.
 18. The flexible vibration module of claim 13, wherein:each of the plurality of piezoelectric portions comprises an inorganicmaterial; and the flexible portion comprises at least one of an organicpiezoelectric material and an organic non-piezoelectric material.
 19. Adisplay apparatus, comprising: a flexible vibration module, including: apiezoelectric composite layer, including: a plurality of piezoelectricportions each having a piezoelectric characteristic, wherein at leasttwo of the plurality of piezoelectric portions have different sizes; anda flexible portion between the plurality of piezoelectric portions; afirst electrode on a first surface of the piezoelectric portions and afirst surface of the flexible portion; and a second electrode on asecond surface of the piezoelectric portions and a second surface of theflexible portion, and a display panel, wherein the display panelcomprises a display area configured to display an image and vibrateaccording to a vibration of the flexible vibration module, wherein eachof the first surface and the second surface is configured to have aplane surface structure.
 20. The display apparatus of claim 19, furthercomprising a touch electrode configured to sense a touch, wherein theflexible vibration module is configured to vibrate according to thetouch.
 21. The display apparatus of claim 19, wherein: each of theplurality of piezoelectric portions comprises an inorganic material; andthe flexible portion comprises at least one of an organic piezoelectricmaterial and an organic non-piezoelectric material.
 22. The displayapparatus of claim 19, wherein: the display panel comprises a firstregion and a second region; the flexible vibration module is a firstflexible vibration module in the first region of the display panel; anda second flexible vibration module is included in the second region ofthe display panel.
 23. The display apparatus of claim 22, furthercomprising: a rear structure on a rear surface of the display panel; andat least one partition member between the display panel and the rearstructure and between the first flexible vibration module and the secondflexible vibration module.
 24. The display apparatus of claim 22,further comprising: a rear structure on a rear surface of the displaypanel; and a partition between the display panel and the rear structure,wherein the partition surrounds at least one of the first flexiblevibration module and the second flexible vibration module.
 25. Thedisplay apparatus of claim 24, further comprising another partitionbetween the display panel and the rear structure, the another partitionsurrounding both the first and second flexible vibration modules, andthe partition.